I've spent some time in order to gather data about formulas and mechanics that could be possibly connected with tanking. This post consist all the most important information collected from various websites, forums, other's experience and my own. Hope it will come helpfull one day.


Attributes

Strength
1 Strength grants 2 Attack Power.
1 Strength grants 0.05 Block Value.
1 Attack Power equals 0.07 dps.

Agility
1 Agility grants 2 Armor Class.
1 Agility grants 0.03 Critical Strike.
1 Agility grants 0.034 Dodge.

Defense Skill
1 Defense Skill grants 0.04 Dodge.
1 Defense Skill grants 0.04 Parry.
1 Defense Skill grants 0.04 Block.
1 Defense Skill grants 0.04 less chance to be Hit.
1 Defense Skill grants 0.04 less chance to be Critically Hit.

Weapon Skill
1 Weapon Skill equals 0.1 Critical Strike chance against monsters above your level.
In addition Weapon Skill wokrs quite opposite to Defense Skill.
Your chance to Miss decreases by 0.04%.
Your chance to score a Critical Hit increases by 0.04%.
Your opponent's chance to Block your attack decreases by 0.04%.
Your opponent's chance to Parry your attack decreases by 0.04%.
Your opponent's chance to Dodge your attack decreases by 0.04%.


Combat Attributes

Defense Rating
1 Defense Rating grants 0.4166 Defense Skill.
This means that:
1 Defense Rating grants 0.0166 Dodge.
1 Defense Rating grants 0.0166 Parry.
1 Defense Rating grants 0.0166 Block.
1 Defense Rating grants 0.0166 less chance to be Hit.
1 Defense Rating grants 0.0166 less chance to be Critically Hit.

Weapon Skill Rating
1 Weapon Skill Rating grants 0.2564 Weapon Skill.

Dodge Rating
1 Dodge Rating grants 0.0539 Dodge.

Parry Rating
1 Parry Rating grants 0.0423 Parry.

Block Rating
1 Block Rating grants 0.1266 Block.

Hit Rating
1 Hit Rating grants 0.0633 Hit.

Critical Strike Rating
1 Critical Strike Rating grants 0.0452 Critical Strike.

Resilence Rating
1 Resilence Rating grants 0.0256 less chance of being struck by any type of Critical Strike.
1 Resilence Rating grants 0.0512 less damage taken from any kind of Critical Strikes.

Haste Rating
1 Haste Rating grants 0.0632 Haste.

Additional Note
In order to check relationship between "Factor Rating" and full percentage value please visit http://www.wow-europe.com/en/info/basics/characters.html I decided to put it in a different way because in my opinion it's easier to compare which item improves you the most by multiplying base values.


Rage Generation

Rage Generated By Dealing Damage:
Damage Dealt multiplyed by 7.5 divided by 274.7.

Rage Generated By Taking Damage:
Damage Taken multipled by 2.5 divided by 274.7.


Migitation

Miss
Attack missed. This event is a 5% standard for mobs and players. There is no percentage limit for this factor. Attacks from behind can miss. You can be missed when stunned. This does not generate rage nor threat.

Dodge
Attack is dodged. This event is a 5% standard for mobs and players. There is no percentage limit for this factor. Attacks from behind can be dodged. You cannot dodge when stunned. This does not generate rage nor threat.

Parry
Attack is parried. This event is a 5% standard for mobs and players. There is no percentage limit for this factor. Attacks from behind cannot be parried. You cannot parry when stunned. When parry occurs it reduces the swing timer of your current swing by 40% of weapon speed to a minimum of 20% of the timer. Parry does not generate rage nor threat.

Shield Block
You block the attack. A number equal to your block value is substracted from the attack. This attack is not a crit, nor a crushing blow, for reasoning see below. This event is a 5% standard for mobs and players. Attacks from behind cannot be blocked. You cannot block when stunned. There is no percentage limit for this factor. Block does generate rage and threat depending on the amount of damage taken.

Crushing Blow
Crushing blows hit for 150% damage. Players can never land crushing blows. Only white damage (auto-attacks) can be crushing blows. Spells and specials like Mortal Strike or Mighty Smash cannot be crushing blows. If your defense skill is at your level maximum, then mobs 3 or more levels above your level can land crushing blows with a basic 15% chance to do so. For every point of defense skill you are under 5 times of your level, the chance of a crushing blow increases by 2%. Defense from gear does affect your chance to receive crushing blows unless your base defense skill is lower than 5 times your level.

Armor

Increases your physical damage migitation according to the formula:

                 Armor             

M = ---------------------------------

    A + (467.5 x Mob Level - 22167.5)

Note that armor mitigation has a percentage capacity of 75.


Level Differances

Just as each level that the mob is above you, increases it's chance to crit by 0.2%, it also reduces it's chance to miss by 0.2%, and your chance to dodge by 0.2%, parry by 0.2%, and block by 0.2%.

Every Raid Instance Boss is level 73. That means chance to crit is increased by by 0.6%, it's chance to miss is reduced by 0.6%, and your chance to dodge by 0.6%, parry by 0.6%, and block by 0.6%.

Therefor a main-tank needs 490 defense skill in order to be immune to critical strikes. 5.6 devided by 0.04 equals 140. 350 defense skill is base value for every level 70 player. 350 plus 140 equals 490 defense skill.


Avoidance Comparison After 490 Defense

Defence Rating
1 Defense Rating grants 0.0166 dodge, 0.0166 parry, 0.0166 block, less chance to be hit, 0.0166 less chance to be critically hit. Since at 490 Defence Skill critical strikes from mobs will be wiped off the Attack Table (see below) and the chance to block is a small bit of mitigation, not actual avoidance, so we'll ignore these two. That translates to 0.050 pure avoidance per point of Defense Rating.

Dodge Rating
1 Dodge Rating grants 0.0539 Dodge.

Parry Rating
1 Parry Rating grants 0.0423 Parry.

Conclusion
It seems like Defence Rating is the best Avoidance Attribute. It's nearly as good as Dodge Rating in pure avoidance. In addition it gives a bit of block chance which alwayas comes handy when our enemy hits fast. In PvP it's also reducing chance to score a critical strike on us.

The Attack Table

The tables are laid out in descending order of the precedence of one attack result over another. The entries at the top of the table take precedence over the entries below them. The order is:
Miss - Dodge - Parry - Glancing Blow (only players vs mobs) - Block - Critical Hit - Crushing Blow (only mobs vs players) - Ordinary Hit.

Some melee attacks have a 0% chance for some of these attack results. An auto-attack made by a player has a 0% chance of being a crushing blow, an attack made by a mob has a 0% chance of being a glancing blow, an attack made against a player without a shield has a 0% chance of being blocked, magic based attacks have 0% chance of being blocked, etc..

For mob and white damage melee attacks, there is no such thing as a blocked crushing blow, a parried critical strike, a missed glancing blow, etc. All of these possible attack results are mutually exclusive.

If the total combined chance of a miss, dodge, parry, or block is 100% or higher not only the attack cannot be an ordinary hit (in worst case it will be blocked), the attack also cannot be a critical strike or a crushing blow.

The Die Roll Theory
In a table based combat system, every possible outcome for an attack is put in a table. Each entry in the table is assigned a numeric range. When an attack is made, a single random number is generated and the result is looked up on the table. Number scored defines the result.

Example:
Let's say that a level 70 Warrior with 490 defense has 20.60% parry, 20.60% dodge, 20.60% block, chance to beign miss incresed by 5.60% and chance of beign a victim of critical strike reduced by 5.60%. Note that values in your spell book are given against mobs the same level you are.

This is how will the attack table look like if he fights a boss in Tempest Keep. Note that Raid Instance bosses are level 73.

Warrior doesn't use Shield Block.

    RESULT       CHANCE       DIE ROLL

    Miss         10.00%     0.01 - 10.00

    Dodge        20.00%    10.01 - 30.00

    Parry        20.00%    30.01 - 50.00

Glancing Blow     N/A           N/A

    Block        20.00%    50.01 - 70.00

  Critical        N/A           N/A

Crushing Blow    15.00%    70.01 - 85.00

Ordinary Hits    100.0%    85.01 - 100.0

Warrior uses Shield Block now.

    RESULT       CHANCE       DIE ROLL

    Miss         10.00%     0.01 - 10.00

    Dodge        20.00%    10.01 - 30.00

    Parry        20.00%    30.01 - 50.00

Glancing Blow     N/A           N/A

    Block        95.00%    50.01 - 100.0

  Critical        N/A           N/A

Crushing Blow    15.00%         N/A     

Ordinary Hits    100.0%         N/A

As you can see, every single attack will be either missed, dodged, parried or blocked. It cannot be a critical strike, neither a crushing blow.


Resistance Table Against Level-73 Direct Damage Spells

Resistance Score            	   73      146    219     292     365

Chance to Resist Spell             0% 	   1% 	   1% 	  11% 	  25%

Chance to Resist 100% Damage       0% 	   1% 	   1% 	  11% 	  25%

Chance to Resist 75% Damage 	   2% 	   6% 	  18% 	  34% 	  55%

Chance to Resist 50% Damage 	  11% 	  24% 	  48% 	  40% 	  16%

Chance to Resist 25% Damage 	  33% 	  49% 	  26% 	  14% 	   3%

Chance to Take Full Damage 	  54% 	  20% 	   7% 	   1% 	   1%

Threat Generation

One point of damage dealt generates one point of threat.

Taunt
The mob is forced to attack you for 3 seconds. Later taunts by other players may override it.

You are permanently given threat equal to the mob's previous aggro target. You won't necessarily get as much threat as the highest person on the mob's list, only as much as whoever is currently tanking it.

You gain complete aggro on the mob at the instant you taunt. Usually you would need 10% more threat to gain aggro, but a taunt now gives you instant aggro on the mob. If other people are generating significant threat on the mob, they could exceed your threat by more than 10% before the taunt debuff wears off, and will gain aggro as soon as it does. There is no limit to the amount of threat you can gain from Taunt.

Challenging Shout and Mocking Blow have a similar forced attack debuff to Taunt. However, they do not give the caster threat in the same way as Taunt. Instead of that, player is proved by fixed amounts that may force mob to attack him for a short period of time.

Stance Convertion
Battle Stance: 80% Threat Convertion.
Defensive Stance: 130% Threat Convertion. Together with Defaince it's 149.5% Threat Convertion.
Berserker Stance: 80% Threat Convertion.

Abilities
Threat listed is a value in addition to the damge that given ability does. Statistics are shown for non-improved skills. These are Raw Values, which means they are not modified by Combat Stances.

Shield Slam (Rank 6)          307

Sunder Armor (Rank 6)         301

Shield Bash (Rank 4)          230

Revenge (Rank 8)              201

Heroic Strike (Rank 10)       196

Hamstring (Rank 4)            181

Disarm                        104

Devastate                     101

Cleave (Rank 6)               130 Split

Battle Shout (Rank 8)         69  Split

Commanding Shout (Rank 1)     68  Split

Demoralizing Shout (Rank 7)   56  Split

Thunder Clap                  +75% of Damage Done

Execute                       +25% of Damage Done

Spell Reflect                 0

Piercing Howl                 0

Concussion Blow               0

Overwriting a buff doesnt affect the threat caused. For example, Sunder Armor causes as much threat when there are 5 debuffs as none, and player buffs cause just as much threat if the player already had one up.

Abilities listed with additional note "Split" divide the generated threat among affected targets. For example, if you perform Demoralizing Shout on two mobs, each mob will get 28 threat. If you perform Demoralizing Shout on three mobs, each will get 18.7 threat.

Good guide, but I think it'd be better if you wrote how much rating is needed for 1% of a particular stat rather than typing how much % 1 rating gives you.

http://www.wow-europe.com/en/info/basics/characters.html

365 is the resistance cap no? boss lvl (73)x5

You didn't mention Agility --> Dodge at the start - you mentionned armour and even crit, but not dodge :P

Good effort.

Yes, include agi -> dodge and add how much "rating" is needed for a whole percentage - then I'll stamp this "Feril approved". :p Nice job btw. :)

omg nerf nerf i got ze kil...ganked by a rog! AMMAGADD WTF!

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Q u o t e:

Dodge
Attack is dodged. This event is a 5% standard for mobs and players. There is no percentage limit for this factor. Attacks from behind can be dodged. You cannot dodge when stunned. This does not generate rage nor threat.

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Attacks from behind cannot be dodged. Proof: http://img527.imageshack.us/img527/8854/dodgeik8.jpg

Screenshot was taken 1 second before evasion fell, no more attacks were made during evasion. The chance of no dodges during that time is (1-0.7)^7 = 0.0002187 = 0.02187%

Unless it functions differently for boss mobs then I think you should correct this, otherwise very nice job and a good effort. Worth the sticky.

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Q u o t e:
A great guide to the benefits of various statistics and the use of threat generating abilities. We will include this in the Forum Watch later today.

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Salthem, while you are here - are there any plans to clean up a bit among the stickies? Every now and then all stickies are unstickied and we're told that they are too many and that we'll need to consolidate them into one or several bigger threads if we wish to keep them stickied... but that never happens (due to laziness or lack of initiative or whatever) and the old stickies are usually simply restickied.

While I agree that this is a quite informative guide, I wonder how adding more stickies helps alleviate the problem with stickies being too many?

This is interesting reading.

Really nice guide, thanks for the compilation.

You might want to add the to hit needed to negate all misses when using 1h+shield. Asfaik the miss chance against a lvl 73 boss is 8.6% for both white hits and special when using 1h+shield (from the theorycrafting thread at Elitist Jerks forum).

I don't think the Weapon Skill factors are correct: a Blue post gave different figures.

Whilst the Blue post was proved not 100% true they gave an indication of the true figures which extensive testing has revealed:

1 Weapon Skill also gives you +0.1% Hit (proben to a massive degree of confidence).
The effect on your opponents Dodge is much higher than it is on Block and Parry (at least double).

The reason for this is that all Mobs/PCs can Dodge but only some can Block and Parry - so loading more of the value onto Dodge retains the "value" of this Skill.

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Q u o t e:
I don't think the Weapon Skill factors are correct: a Blue post gave different figures.

Whilst the Blue post was proved not 100% true they gave an indication of the true figures which extensive testing has revealed:

1 Weapon Skill also gives you +0.1% Hit (proben to a massive degree of confidence).
The effect on your opponents Dodge is much higher than it is on Block and Parry (at least double).

The reason for this is that all Mobs/PCs can Dodge but only some can Block and Parry - so loading more of the value onto Dodge retains the "value" of this Skill.

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Wasn't it the other way around? That bosses roughly had a 15% chance to parry and 5ish % chance to dodge, hence why weapon skill reduced parry much more than dodge, making it a very good tank stat since only frontal attacks can trigger parry?

Here's the text of the original blue post:

"
Originally Posted by Crezax
Let's say you increase your weapon skill by 4.

Against a mob 3 levels higher than you, you get: 0.8% lower chance to miss, 0,4% lower chance to get dodged, 2,4% to be parried, and a 0,8% higher chance to crit.
"

You are correct he indicated Parry was the most affected stat. However people have been doing extensive testing and Crezax figures have been disproved (it certainly needs clarification for white / yellow damage) whilst it appears that it's definately Dodge which is affected more.
Some think that Block and Parry are entirely unaffected and instead got lumped into the Dodge modifier.

Weapon Skill itemization is aimed at nonTanks too - you find Weapon Skill present in the Warrior Arms and Rogue Combat trees too for example.
When the effect on Glancing was (apparently) removed people initially thought Weapon Skill had become a poor rating but Rogues later found it was still very good for their PvE DPS (I would go so far as to say they now believe that +10 Weapon Skill is a must).

Summary of the many, many posts I've read following various tests such as 10,000 swing tests v same level Mobs:

+1 Skill (not rating!) gives.
+0.1% Hit
+0.4% Crit
Some effect on Dodge :)
Very little to no affect on Parry/Block

It's still something nobody can nail and we just wish Blizzard would confirm it or indeed Crezax could clarify/expand on what he said.

We used to know what Weapon Skill did and now we just know that it's "good" but vague on exactly how it is good :)

PS: I wish to credit the posters at Elitist Jerks for this testing and maths, I'm just following it and attempting to summarize it.

Yup, although I figured that weapon skill might've been changed since Crezax posted that, just like it was changed some time after it was nerfed. Prior to his post it used to increase your chance to crit bosses by 0.1% per skill point or something equally weak, that's why his post came as something of a surprise to most people at that time.

People on he EJ forums tested weapon skill out in an attempt to verify the information Crezax supplied and concluded that it did in fact reduce mob avoidance by about 1% per weapon skill (tests done over a full Karazhan run). Not sure how much has changed since, or if the avoidance part was moved from parry to dodge, or if the assumption that parry was reduced so much was merely theorycraft to begin with.

The warrior/rogue weapon skill talents were added while weapon skill still reduced glancing blows, if I'm not mistaken. Just before weapon skill was nerfed.

Nevertheless, thanks for the post. :)

nice work Incubo

Devastate causes an amount of threat for each application of Sunder Armor, so there should be 5 Devastates in ur Threat list. Besides that, GREAT guide! It really made some things clear I wanted to know, good work

To make it easier to understand how does the Weapon Skill work i'll ignore it's Critical Srike bonus and focus on the relation with Defense Skill.

Since Defense Skill increases avoidance based on comparision with enemie's Weapon Skill it seems quite logical that Weapon Skill does the opposite.

A player with 350 Weapon Skill is fighting a level 70 mob with 350 Defense Skill. Differance between Weapon Skill and Defense Skill equals 0. The creature will have no bonus avoidance against that player.

A player with 350 Weapon Skill is fighting a level 71 mob with 355 Defense Skill. Differance between Weapon Skill and Defense Skill equals 5. The creature will have 1% of total bonus avoidance against that player.

A player with 355 Weapon Skill is fighting a level 70 mob with 350 Defense Skill. Differance between Weapon Skill and Defense Skill equals 5. The creature will have it's avoidance reduced by total value of 1% against that player.

A player with 355 Weapon Skill is fighting a level 70 mob with 350 Defense Skill. Differance between Weapon Skill and Defense Skill equals 0. The creature will have no bonus avoidance against that player.

We are all aware of what Crezax wrote. However, nobody knows where did he get these values from. There is no explenation given, no feedback, nothing.

As for the Devastate,
Bonus threat given by this ability is not affected by Sunder Armor. However, the demage Devastate does is. Therefor, you deal more damage when the target has multiply Sunder Armors on him, which turns into more threat.