From The Fluid Druid with my notes in Red:
What is the combat table?
Every time you attack an enemy, WoW creates a hit table for that attack that determines the result. There are two different systems, one for standard melee (or white) attacks, and one for special (or yellow) attacks. We’ll look at the standard table, and then see how yellow attacks differ. Also note that these numbers are only for level 83/boss mobs.
White Attack Table:
Miss: Your character has a base 8% chance to miss. This is mitigated by Hit Rating. 32.8 points of +Hit will reduce this chance by 1%, so you need 263 +Hit to be hit-capped, or reduce your miss chance to 0%. A Draenei in your party adds a 1% hit aura, reduces the hit cap to 230. Any hit above cap is wasted in terms of melee attacks (though it does help for spells and taunts.)
Dodge: Your character has a base 6.5% chance to have its attack dodged. This is mitigated by Expertise Rating. (Expertise Rating is the number displayed on gear and on the tooltip when you mouseover; expertise skill is the displayed value.) 32.8 points of Expertise Rating (which equals 4 expertise skill) will reduce this chance by 1%, so you need 214 Expertise Rating (26 expertise skill) to be expertise-capped, or reduce your dodge chance to 0%. If you are talented into Primal Precision (and you should be as a feral DPS’er), that gives you 83 points of Expertise Rating (10 expertise skill), which reduces the expertise cap to 131.
Parry: Your character has a 14% chance to have its attack parried. This can be reduced by expertise, or eliminated completely by attacking the mob from the rear (so always attack from the rear). This is also why expertise is so good for a tank’s threat generation, as they are forced to attack from the front.
Glancing Blow: Your character has a 24% chance to have its attack be a “glancing blow.” This does less damage than a normal attack, but more importantly, there is no way to mitigate glancing blow chance.
Block: Your character has a 5% chance to have its attack blocked. This can be eliminated by attacking from the rear. (I’m not sure if this falls on the combat table, or if you simply have a 5% chance to have a crit/hit blocked if attacking from the front. Either way, it’s not really relevant to a DPS discussion, as we’re attacking from the rear regardless.)
Crit: Your critical strike chance. Against a level 83/boss mob, 4.8% of your crits are reduced to hits. (This was previously thought to be a crit reduction; however, it has since been shown that it is a conversion, and therefore cannot be mitigated. EDIT: It’s now a crit reduction again.)
Hit: If an attack doesn’t fall into one of the previous categories, it’s a standard hit.
So how does this work?
For every white attack, the WoW engine builds a hit table using the above stats, and rolls a 1-100 to see where that attack lands on the hit table. Let’s use an example to show how this works.
I have 0 hit, 0 expertise, no Primal Precision talent, and 50% crit, attacking a boss from the rear. The hit table would look like this:
1-8: miss
9-15.5: dodge
15.5-15.5: parry (eliminated due to attacking from the rear)
15.5-39.5: glancing blow
39.5-85.7: crit
85.7-90.5: hit (crit reduction)
90.5-100: hit
Yellow attacks are slightly different, as they follow a two-roll system. For each attack, the game rolls once to determine if the attack hits (100% – miss/dodge/parry chance). If the attack hits, the game rolls again to determine if the attack is a crit. The jury is still out on this, but it appears that the crit conversion is simply a crit reduction for yellow attacks, so 104.8% crit should give you 100% crit on yellow attacks.
Why is this important?
Well, looking at the example above, extra crit will only convert that bottom 9.5% of white hits to crits. Anything over that is wasted for white attacks. Put another way, with full hit and expertise, the crit cap is 76% (100% – glancing blows.) With no hit or expertise, the crit cap drops to 60.5%. This isn’t that hard to reach; my average crit self-buffed is about 55% before procs. Depending on your gear and situation (raidbuffs), this can devalue agility and crit for gemming/enchanting/trinkets. (Death’s Verdict is the worst for this.) Yellow attacks don’t have to deal with glancing blows, so the crit cap for those is 95.2%, or 79.7% with no hit/expertise. (EDIT: These are ACTUAL numbers…apologies for not being more clear. Your character pane numbers will be 4.8% higher than actual, since they assume attacking a same-lvl mob. For example, your character pane critcap would be 80.8%.)
A good way to judge how each type of hit is played out in your own boss fights is to look at World of Logs. If your guild doesn't log runs, then you should start, it's a great tool. In order to evaluate your hits using WoL, go to a nongimic fight, like saurfang for melee, choose damage done, and choose yourself from the list of raiders. Look first at your uptimes in the buffs cast section (here's one of mine), and then look at your Damage by Spell. If you hover your mouse over my melee swings you will get a breakdown of all the melee hit table. Notice here that I have misses, hits, crits, etc. The parries are likely from when saurfang turns around to cast. Looking at this I can see that I am not crit capped because I still have hits. Once all of those hits go away then I know I'm crit capped. If I still have misses at that point, then getting more hit will start bringing back those hits and with enough crit, make them crits. The object is to get it down till your hit table consists of ~24% glancing blows and ~76% crits.
So what do I do?
First of all, nothing drastic. Agility is still a good stat, since it will continue to increase your yellow crit rate, and it only devalues slightly if you’re over the crit softcap (from procs). However, if you are in an environment where you can count on being over the white crit hardcap, then it’s probably time to regem, probably to ArPen for reds (if not capped) and agi/haste, agi/expertise, or agi/hit for yellows. I’ll explore this more in a later post. Secondly, if you’re not hit/expertise capped, those stats become MUCH more valuable past the crit cap, as each miss/dodge is almost always a missed crit. We were swimming in hit in previous tiers; now, it’ll be much harder to come by.
Happy Shredding!
