Link to the Primary Source:
Preventing Crushing Blow and Regular Hit:
At the above examples, you can see the basic principle of pushing Crushing Blow and Regular Hit off the table. By raising your total Miss, Dodge, Parry and Block chance to 100% or higher, there is not space left for Critical Hit, Crushing Blow and Regular Hit.
A Protection Warrior's Shield Block adds 75% Block chance to 2 blocks per 5 seconds. Protection Warriors only need 25% additional mitigation chance to reach 100%, which they already receive from base values and talents. Warriors without the Improved Shield Block talent can only use Shield Block for 1 block per 5 seconds, which results in it being down often, leaving the Warrior vulnerable to Critical Hit, Crushing Blow and Regular Hit.
A Protection Paladin's Holy Shield adds 30% Block chance to 8 blocks per 10 seconds. The Libram of Repentance raises this by 5.31%. Protection Paladins need 65% additional mitigation chance to reach 100%. They receive around 25% from base values and talents, so about 40% more needs to come from gear (excluding the Libram of Repentance). Protection Paladins also have Redoubt, which adds 30% Block chance to 5 blocks for 10 seconds. However, Redoubt is a chance result of getting hit and cannot be kept up permanently, making it ineffective to reliably prevent Critical Hit, Crushing Blow and Regular Hit.
Druids cannot Parry or Block, so they can only use Miss and Dodge. They have no skills that drastically raise these stats and thus cannot prevent Critical Hit, Crushing Blow and Regular Hit in this way.
The mentioned method is quite situational. There are certain situations where this will not work, leaving you vulnerable to Critical Hit, Crushing Blow and Regular Hit:
- Mobs attack you in the rear. - Mobs use ranged attacks. - Mobs attack you more often than Shield Block (2 blocks per 5 seconds) or Holy Shield (8 blocks per 10 seconds) can sustain. - You get stunned and cannot keep Shield Block or Holy Shield up. - You get silenced and cannot keep Holy Shield up. - You do not have enough rage or mana to recast Shield Block or Holy Shield. - Holy Shield gets dispelled. - You are disarmed and cannot Parry. - You are casting and cannot Block.
For Crushing Blows and Regular Hits, nothing else can be done. Raising your total Miss, Dodge, Parry and Block chance to 100% or higher is the only method to prevent them. There is however a different solution for Critical Hits, that is more reliable.
Preventing Critical Hit:
Critical Hit% = 5% + ((Attacker's Weapon Skill) - (Defender's Defense Skill)) * 0,04%
For the average mob or character, both Weapon Skill and Defense Skill are 5*lvl. So if both the attacker and defender are of equal level, without bonuses to Weapon Skill or Defense Skill, the Critical Hit chance is 5%. Bosses are always considered 3 levels higher than you, so their Weapon Skill is 15 higher than your default Defense Skill, which raises the Critical Hit chance by 0.6% (to 5.6%).
By raising the Defense Skill high enough to reduce this chance by 5.6%, the Critical Hit chance from bosses is reduced to 0%. This requires 140 additional Defense Skill (which, at level 70, brings you to 490 Defense Skill). For level 70 characters, 2.4 Defense Rating raises your Defense Skill by 1. 336 Defense Rating raises your Defense Skill by 140.
Warriors and Paladins have a talent called Anticipation that raises their Defense Skill by 20. Characters with this talent only need an additional 120 Defense Skill. 288 Defense Rating raises your Defense Skill by 120.
Druids:
Druids have a talent called Survival of the Fittest that reduces the Critical Hit chance against them by 3%. Characters with this talent reduce the Critical Hit chance from bosses down to 2.6%. Reducing the Critical Hit chance by 2.6% requires 65 Defense Skill (which, at level 70, brings you to 415 Defense Skill). 156 Defense Rating raises your Defense Skill by 65.
For Druids, every point of Defense Skill: - Increases the chance to be Missed by 0.04%. - Increases the chance to Dodge by 0.04%. - Decreases the chance to receive a Critical Hit by 0.04%.
Once 415 Defense Skill is reached, only complete avoidance helps. To upgrade complete avoidance by 1%, you need: - 14.7 Agility (Druid) - 18.9 Dodge Rating - 30 Defense Rating (Druid)
Calculations:
As mentioned above, you need 490 Defense Skill to prevent Critical Hits from bosses. In addition, you need to raise the total Miss, Dodge, Parry and Block chance against lvl73 mobs to 100% to prevent Crushing Blows and Regular Hits from bosses. Warriors and Paladins can achieve this. Druids cannot.
For the sake of simplicity, I'm going to assume you do not have talent points in Deflection, Anticipation or Warrior Shield Specialization.
Base Agility @ lvl70: Night Elven Warrior - 101 Human Warrior - 96
Human Paladin - 77 Dwarven Paladin - 73 Draenei Paladin - 74 Blood Elven Paladin - 79
Miss chance:
For Warriors and Paladins, every point of Defense Skill: - Increases the chance to be Missed by 0.04%. - Increases the chance to Dodge by 0.04%. - Increases the chance to Parry by 0.04%. - Increases the chance to Block by 0.04%. - Decreases the chance to receive a Critical Hit by 0.04%.
2.4 Defense Rating = 1 Defense Skill (@ lvl70) 60 Defense Rating = +1% Miss, +1% Dodge, +1% Parry, +1% Block, -1% Crit (@ lvl70)
Miss% = 5% + ((Defenders Defense Skill) - (Attackers Weapon Skill)) * 0.04% Miss% = 5% + (Defense Rating / 60)% (+0.8% with Anticipation) (-0.6% against lvl73 mobs)
Dodge chance:
18.9 Dodge Rating = 1% Dodge (@ lvl70) Night Elves have a 1% Racial Bonus to Dodge%.
Dodge% = Base Dodge% + Racial Bonus + (Dodge Rating / 18.9)% + ((Defenders Defense Skill) - (Attackers Weapon Skill)) * 0.04% + (Agility / Agility Ratio)% Dodge% = Base Dodge% + (Dodge Rating / 18.9)% + (Defense Rating / 60)% + (Agility / Agility Ratio)% (+1% for Night Elven Warriors) (+0.8% with Anticipation) (-0.6% against lvl73 mobs)
Warriors (Base Dodge% = 0.75%, Agility Ratio = 30): Dodge% = 0.75% + (Dodge Rating / 18.9)% + (Defense Rating / 60)% + (Agility / 30)% (+1% for Night Elven Warriors) (+0.8% with Anticipation) (-0.6% against lvl73 mobs)
Night Elven Warrior (Base Agility = 101, Racial Bonus = 1%): Dodge% = 4.91% + (Dodge Rating / 18.9)% + (Defense Rating / 60)% + (Agility Bonus / 30)% (+0.8% with Anticipation) (-0.6% against lvl73 mobs)
Human Warrior (Base Agility = 96, other Warriors match this closely): Dodge% = 3.75% + (Dodge Rating / 18.9)% + (Defense Rating / 60)% + (Agility Bonus / 30)% (+0.8% with Anticipation) (-0.6% against lvl73 mobs)
Paladins (Base Dodge% = 0.65%, Agility Ratio = 25): Dodge% = 0.65% + (Dodge Rating / 18.9)% + (Defense Rating / 60)% + (Agility / 25)% (+0.8% with Anticipation) (-0.6% against lvl73 mobs)
Human Paladin (Base Agility = 77, other Paladins match this closely): Dodge% = 3.53% + (Dodge Rating / 18.9)% + (Defense Rating / 60)% + (Agility Bonus / 25)% (+0.8% with Anticipation) (-0.6% against lvl73 mobs)
Parry chance:
22.4 Parry Rating = 1% Parry (@ lvl70) Deflection gives a 5% Talent Bonus to Parry%.
Parry% = 5% + Talent Bonus + (Parry Rating / 22.4)% + ((Defenders Defense Skill) - (Attackers Weapon Skill)) * 0.04% Parry% = 5% + (Parry Rating / 22.4)% + (Defense Rating / 60)% (+0.8% with Anticipation) (+5% with Deflection) (-0.6% against lvl73 mobs)
Block chance:
7.9 Block Rating = 1% Block (@ lvl70) Warrior Shield Specialization gives a 5% Talent Bonus to Block%.
Block% = 5% + Talent Bonus + (Block Rating / 7.9)% + ((Defenders Defense Skill) - (Attackers Weapon Skill)) * 0.04% + Ongoing skill effects Block% = 5% + (Block Rating / 7.9)% + (Defense Rating / 60)% (+0.8% with Anticipation) (+5% with Warrior Shield Specialization) (-0.6% against lvl73 mobs) (+75% with Shield Block) (+30% with Holy Shield (+5.31% with Libram of Repentance)) (+30% with Redoubt)
Warriors: Block% = 5% + (Block Rating / 7.9)% + (Defense Rating / 60)% (+0.8% with Anticipation) (+5% with Shield Specialization) (-0.6% against lvl73 mobs) (+75% with Shield Block)
Paladins: Block% = 5% + (Block Rating / 7.9)% + (Defense Rating / 60)% (+0.8% with Anticipation) (-0.6% against lvl73 mobs) (+30% with Holy Shield (+5.31% with Libram of Repentance)) (+30% with Redoubt)
Prevention chance:
Chance to prevent Crushing Blow and Regular Hit: [Miss%] + [Dodge%] + [Parry%] + [Block%]
[5% + (Defense Rating / 60)% (+0.8% with Anticipation) (-0.6% against lvl73 mobs)] + [Base Dodge% + (Dodge Rating / 18.9)% + (Defense Rating / 60)% + (Agility / Agility Ratio)% (+1% for Night Elven Warriors) (+0.8% with Anticipation) (-0.6% against lvl73 mobs)] + [5% + (Parry Rating / 22.4)% + (Defense Rating / 60)% (+0.8% with Anticipation) (+5% with Deflection) (-0.6% against lvl73 mobs)] + [5% + (Block Rating / 7.9)% + (Defense Rating / 60)% (+0.8% with Anticipation) (+5% with Warrior Shield Specialization) (-0.6% against lvl73 mobs) (+75% with Shield Block) (+30% with Holy Shield (+5.31% with Libram of Repentance)) (+30% with Redoubt)]
15% + Base Dodge% + (Defense Rating / 15)% + (Dodge Rating / 18.9)% + (Parry Rating / 22.4)% + (Block Rating / 7.9)% + (Agility / Agility Ratio)% (+1% for Night Elven Warriors) (+3.2% with Anticipation) (+5% with Deflection) (+5% with Warrior Shield Specialization) (-2.4% against lvl73 mobs) (+75% with Shield Block) (+30% with Holy Shield (+5.31% with Libram of Repentance)) (+30% with Redoubt)
Night Elven Warriors: 19.91% + (Defense Rating / 15)% + (Dodge Rating / 18.9)% + (Parry Rating / 22.4)% + (Block Rating / 7.9)% + (Agility Bonus / 30)% (+3.2% with Anticipation) (+5% with Deflection) (+5% with Shield Specialization) (-2.4% against lvl73 mobs) (+75% with Shield Block)
Human Warriors (Other Warriors match this closely): 18.75% + (Defense Rating / 15)% + (Dodge Rating / 18.9)% + (Parry Rating / 22.4)% + (Block Rating / 7.9)% + (Agility Bonus / 30)% (+3.2% with Anticipation) (+5% with Deflection) (+5% with Shield Specialization) (-2.4% against lvl73 mobs) (+75% with Shield Block)
Human Paladins (Other Paladins match this closely): 18.53% + (Defense Rating / 15)% + (Dodge Rating / 18.9)% + (Parry Rating / 22.4)% + (Block Rating / 7.9)% + (Agility Bonus / 25)% (+3.2% with Anticipation) (+5% with Deflection) (-2.4% against lvl73 mobs) (+30% with Holy Shield (+5.31% with Libram of Repentance)) (+30% with Redoubt)
Warriors:
Warriors do not have to worry about Crushing Blow and Regular Hit. As long as Shield Block is up, Crushing Blow and Regular Hit cannot happen. Their main priority is to get their Defense Skill up to 490. If they have the Anticipation talent, then this requires 288 Defense Rating, else it takes 336 Defense Rating. Additional Block chance is useless, as it falls of the table. Therefore, once 490 Defense Skill is reached, only complete avoidance helps. To upgrade complete avoidance by 1%, you need: - 18.9 Dodge Rating - 20 Defense Rating (Warrior and Paladin) - 22.4 Parry Rating - 30 Agility (Warrior)
Of course there are situations where you cannot keep Shield Block up. In these situations Block Chance has an effect. However, keep in mind that Regular Hit is the first value to fall off. The only effect is that you turn Regular Hit into Block. The damage mitigation is equal to [the difference in Block Chance] * [your Block Value].
Paladins:
Unlike Shield Block, Holy Shield does not push Crushing Blows off the table by itself. Additional prevention is required. Their main priority is to get their Defense Skill up to 490. If they have the Anticipation talent, then this requires 288 Defense Rating, else it takes 336 Defense Rating. Human Paladins with Holy Shield up and 490 Defense (with or without Anticipation) have the following Crushing Blow prevention against a level 73 mob: 68.53% + (Defense Rating beyond 490 Defense / 15)% + (Dodge Rating / 18.9)% + (Parry Rating / 23.7)% + (Block Rating / 7.9)% + (Agility Bonus / 25)% (+5% with Deflection) (+5.31% with Libram of Repentance) (+30% with Redoubt)
Human Paladins need an additional 31.47% chance to prevent Crushing Blow and Regular Hit. To upgrade Crushing Blow prevention by 1%, you need: - 7.9 Block Rating - 15 Defense Rating (Warrior and Paladin) - 18.9 Dodge Rating - 22.4 Parry Rating - 25 Agility (Paladin)
For the sake of simplicity, let's assume you have the Anticipation and Deflection talents maxed out and have the Libram of Repentance equipped (these are mandatory in your early days of fighting Crushing Blow, though you can possibly replace these later on). Since Redoubt is unreliable, I'll stop including it into calculations. If you managed to get 288 Defense Rating from gear, your avoidance will be: 78.84% + (Defense Rating beyond 288 / 15)% + (Dodge Rating / 18.9)% + (Parry Rating / 23.7)% + (Block Rating / 7.9)% + (Agility Bonus / 25)%
That is 21.16% short of Crushing Blow immune. To reach 100% prevention of Crushing Blow and Regular hit while remaining immune to Critical Hits, you need: - 288 Defense Rating + 168 Block Rating - 288 Defense Rating + 318 additional Defense Rating = 606 Defense Rating - 288 Defense Rating + 400 Dodge Rating - 288 Defense Rating + 474 Parry Rating - 288 Defense Rating + 529 Agility Bonus
Of course, you can use a combination of Block Rating, additional Defense Rating, Dodge Rating, Parry Rating and Agility Bonus, as long as the following formula gives a result of 21.16% or higher: (Block Rating / 7.9)% + (Defense Rating beyond 288 / 15)% + (Dodge Rating / 18.9)% + (Parry Rating / 22.4)% + (Agility Bonus / 25)%
Dwarven Paladins need 21.32%. Draenei Paladins need 21.28%. Blood Elven Paladins need 21.08%.
If 100% prevention is reached, additional Block chance becomes useless, as it falls of the table. Therefore, once 490 Defense Skill and 100% prevention are reached, only complete avoidance helps. To upgrade complete avoidance by 1%, you need: - 18.9 Dodge Rating - 20 Defense Rating (Warrior and Paladin) - 22.4 Parry Rating - 25 Agility (Paladin)
Of course there are situations where you cannot keep Holy Shield up. In these situations Block Chance has an effect. However, keep in mind that Regular Hit is the first value to fall off. When Redoubt is not up, the only effect is that you turn Regular Hit into Block. The damage mitigation is equal to [the difference in Block Chance] * [your Block Value].
When Redoubt is up however, there's a slim chance that you receive a Crushing Blow and no chance that you receive a Regular Hit, as Holy Shield has a slightly higher Block Chance than Redoubt due to the Libram of Repentance. Additional Block Chance would actually turn Crushing Blow into Block in those situations.
Checking immunity to Crushing Blow:
There's a simple method to check if you're immune to Crushing Blow or not. You can calculate this from the Defense tab on either your ingame characters sheet or your armory character sheet. Note that bonuses from buffs affect these values directly, so make sure you are unbuffed before starting the calculation.
Hover your mouse over the Defense line. It lists your Miss chance from Defense. Add 5% base Miss chance to this value. Add your Dodge chance. Add your Parry chance. Add your Block chance. Note, if you are in game, it's best to cast Shield Block or Holy Shield right before checking your Block chance. If you cannot do that (for example, you're using the armory), then add the following: - Warrior: 75% for Shield Block. - Paladin: 30% for Holy Shield. - Paladin: 5.31% for Libram of Repentance.
If the total is 102.4% or higher, then you're immune to Crushing Blow (as long as Shield Block or Holy Shield is up of course).
You need to surpass 102.4% instead of 100%, since the character screen assumes you're fighting a lvl 70 mob. A level 73 mob lowers your Miss, Dodge, Parry and Block chance by 0.6% each for a total of 2.4%.
If you follow the link (top) to the primary source you will see lists of tanking gear and its stats.