What is a Block?
Where dodge and parry are damage avoidance (you avoid the entire effect of an attack), a block is mitigation (you avoid some of the effect of an attack). You
have a chance to block, just like you have a chance to dodge and parry, and your chance to block can be increased by effects from items (
Equip: Increases your block rating by 23) or by increasing your defense skill (+0.04% chance to block for each point of defense). Any time you are attacked, your chance to block is included in the
combat table the mob has against you. If the number comes up as a a block, then you block. Simple! You can see your chance to block by hovering over the block icon in your abilities book. Also note that you can only block physical damage, not elemental (fire, arcane, frost, etc.) damage. As an example, using a shield against Baron Geddon is completely useless unless your shield gives you fire resistance, because all of his attacks are pure fire damage.
Block Value? Block Rating? Block Value: How much you block for.
Block Rating: Your chance to block an attack. As always, a rating converts into a game mechanic number. In the case of blocking, divide your block rating by X to get how much chance to block that translates into. At level 70, X is 7.9, so if you have 100 block rating, that adds 12.65% chance to block at level 70.
So What's My Block Value?
As of patch 2.3, mouse over your Block chance in the character window and it'll be in the tooltip.
How Does it Work?
When you block, your block value is subtracted from the damage you would have taken from the attack. Suppose you have 60% mitigation and the block value above. An attack of 1000 damage would be mitigated to 400 damage by your armour. If you don't block, you will take 400 damage (and your combat log reads
Mob hits you for 400 damage). If you do block, you will take 278 damage, and your combat log will read
Mob hits you for 278 damage. (122 blocked)
If you block an attack where your block value is greater than or equal to the amount of damage, you get a full block. So, if some mob would hit you for 85 damage and you get a block on the attack you would see in your combat log:
Mob attacks. You block., and you take no damage from the attack. It used to be that if you got a block against a special attack such as Mortal Strike or the like, it would be a full block no matter how much damage the attack was was for. This was changed quite a long time ago and is no longer the case.
Shield Slam
Also remember that your block value translates directly into Shield Slam damage. If you make up a gear set specifically for Shield Slam, it serves a dual purpose as a soloing set and a high-threat set. Shield Slam crits for 1500 damage (you need about 400 block value) look like DPS. More importantly for tanking, Shield Slam crits for 1500, when combined with the innate threat of Shield Slam, approach 2000 threat per hit. 2000 threat! People have gone out and really pushed their talent build and gear set to optimise Shield Slam, and we've seen screenshots of 3-4k Shield Slam crits. Not only is that a lot of damage, it's a ton of threat. Good times. Other tidbits about Shield Slam:
- 1 block value adds 1 to Shield Slam damage
- Shield Slam crits as per your melee crit chance
- Shield Slam crits are double damage
- One handed weapon specialisation applies to Shield Slam
- Shield Mastery indeed does increase your block value, and so also increases Shield Slam damage
- Impale, Enrage, and Deathwish apply to Shield Slam
- Shield Slam damage is mitigated by armour
The Shield Block Ability
The Shield Block ability gives you a buff that increases your chance to block a single attack by 75% for 5 seconds. If you block an attack during the 5 seconds, the Shield Block buff fades. If you go 5 seconds without blocking, the buff fades. Sticking a talent point in the Improved Shield Block talent extends the buff an extra second, but more importantly grants you +75% chance to block an additional attack (more on this later).
An interesting thing about the Shield Block ability is that adding 75% to your chance to block generally removes the chance of critical hit from the combat table (assuming you had any chance to be crit left after defense.) It's still theoretically possible to be left with a chance for a normal or critical hit in the table, but if your normal chances to be: missed 5%, dodge 15%, parry 15% and block 15% - that adds up to 50% right there. When you add 75 from shield block, you suddenly end up with 5% miss, 15% dodge, 15% parry, and 65% block (and 25% block chance from Shield Block is not used.) There is no room left for a critical hit. Or a regular hit, for that matter. Precedence on the combat table is covered in the
combat table article
On a related note, if the phrase
60% avoidance cap is floating through your mind right about now, please let that old dead horse get its rest. Blizzard has said it's false. We've tested it to be false. You can test it to be false all by yourself if you won't take the word of we who do this testing and number crunching. Let it die already.
An even more interesting thing about Shield Block: It pushes the chance to receive a crushing blow right off the table. Is that important? Yes. Yes it is. A point in Improved Shield Block doubles the effect of this. In fact, on many boss type fights, if you have Improved Shield Block, are diligent about putting up Shield Block when it refreshes, and everything goes right (see [link to crits and crushes]), you can tank the entire fight without taking even one crushing blow. Not only well worth the talent point, but given how hard bosses hit these days before the 150% boost of a crushing blow, it is a
de facto requirement for successfully tanking raids.
Let's talk about avoidance and Shield Block a bit. If you've read [link to combat table] you know about the combat table precedence. It has an important implication. When you have Shield Block up, you have two charges (or one if for whatever daft reason you did not take Improved Shield Block) where you can't take a crushing blow. Since dodge and parry take precedence over block in the combat table, the more of them you have, the more likely you are to dodge or parry while Shield Block is up, extending the amount time you have the buff up before its charges get used. This is a good thing. It means you are taking fewer crushing blows. Not to mention that when Shield Block is not up, you simply avoid a bit more damage to begin with, which could mean that the crushing blow that does get through may not endanger you and your raid.
Do I Need 25% Block?
No. No. No. Miss, dodge and parry take precedence on the combat table over block, so adding 75% block with Shield Block will not remove them from the table (easily verifiable, just pop up Shield Block and watch yourself dodge, parry, and be missed even still.) So, what you need is 25% combined miss+dodge+parry+block. Add 75% for Shield Block, and there you go. If you have 25% combined miss, dodge, and parry, you don't need any block at all, in fact. Since almost all tanking warriors have 490 defense (22.5% combined dodge, block, parry, miss), if you have the deflection or shield specialisation talent, you are good to go without adding anything at all.
Wait, shouldn't that be 27.4%?
Very good! You are in fact correct.
Oh look, the combat table. Now get yourself a cookie for noticing =)
Can I Block Critical Hits?
Short answer: In PvE you don't block critical hits. In PvP you can.
In PvE, the block, critical hit, and crushing blow entries on the combat table are independent entries. When the random number is generated, the result has to be one or the other or the other. A great deal of parsed combat data from a lot of players supports this, showing that no critical hit from a mob has been blocked by a player.
If you've got a screenshot of you blocking a critical hit dealt by a mob, we really want to see it! (email it to me please)
In PvP, the case is definitely different, as shown by numerous screenshots. Right off the top, when a rogue with Cold Blood active hits a warrior with Shield Block active, the hit must be a critical hit because of how Cold Blood works, and it's extremely likely that the hit will be blocked given how Shield Block works. So, we see a blocked critical hit. Beyond that, what we are seeing in screenshots and parsed combat logs is that any white damage attack that is a critical hit cannot be blocked as well, just as in PvE. On the other hand, yellow damage attacks (heroic strike, backstab, mortal strike, etc.) that are critical hits can be blocked - and this is what we have people showing screenshots of. People on the Elitist Jerks forums have some parsing evidence that supports a two table model for yellow damage attacks in PVP. Still haven't seen anyone provide a screenshot of a white damage crit being blocked, but if you have one, please email me!
How much does it help?
If you don't have the Improved Shield Block talent, your block will mitigate from 1-5% depending on your block value and what you are fighting - assuming you pop Shield Block when it cools down. Don't forget that you will take fewer crushing blows as well. This will actually drop you below the 15% minimum. That's something that Paladins and Druids do not have. If you have a point in Improved Shield Block, you can see that jump even higher, especially once your block value breaks 200 points (and again, depending on what you are fighting - your shield gives zero mitigation from blocking against Baron Geddon). Improved Shield Block + Shield Block spam on a world boss = more crushing blows you didn't take than without Improved Shield Block.
