Ever wondered what the deal is with hit rating? Is expertise giving you a bit of a headache? TheoryCraft 101 has all your answers and more, as we explore the depths of the melee hit table.

Back by popular demand, and loads of begging on my part, TheoryCraft 101 is here once again to teach you the ins and outs of the fickle little systems that drive World of Warcraft. Due to numerous requests, we'll be tackling one of the more complex systems within the game, the melee hit table. For all of the hate that armor penetration has taken for being "too mathy," melee hit honestly isn't any better. Caster hit is very simplistic. You have a specific chance to miss a mob, and getting more hit mitigates that amount. Melee hit holds very different values than that. Why just talk about it? Saying that it's complex is all well and good, but let's actually see it, shall we?

As a preface to every TheoryCraft 101 installment, this post is going to contain calculations, figures, theoretical values/situations and other math-related information that, at times, can get a bit confusing. I will always attempt to simplify everything to the best of my abilities and explain the information as clearly as possible. After reading, if you still have any questions about the topic, then just ask. I'll do my best to address every question that you may have.
The auto attack table

Miss

Dodge

Parry

Glancing Blow *

Block

Critical Hit

Crushing Blow **

Hit

To the left is the attack table which dictates every melee swing made by players, pets and mobs within the game. Every attack made generates an internal roll on the server, much like doing a /roll 100, that is then compared against this list. The list itself is displayed in order of precedence. In this case, precedence means that each item at the top of the list will occur before any item at the bottom of the list. That is to say, the server will first check against your chance to miss, then dodge, parry and so on until it gets to the end of the list. It should also be mentioned that every result is mutually exclusive to any other result. This means, you cannot get a blocked critical hit, nor a glancing critical hit. A hit will either be blocked, glancing or a crit. There are some cases where a specific result can be set to 0%. Beyond gearing (which can reduce miss, dodge and parry to 0), there are several situations which can also change the chance of some results:

• Only attacks made by players and pets can be glancing blows; an NPC is not capable of landing a glancing blow.
• Only NPCs are capable of landing a crushing blow; players and pets will never be able to land a crushing attack.
• Mobs cannot parry or block attacks made behind them.
• Players cannot dodge, parry or block attacks made behind them.
• There is 0.5-yard grace distance to determine whether an attacker is behind a target or not, in which all attacks occur from the front even if the attacker is technically standing behind the target.
• Incapacitated targets cannot dodge, parry or block attacks.

As stated, once an attack roll is made, the resultant is then compared against each possible outcome on the list. The list of possibilities continues until it reaches 100%. If the possible outcomes reach 100% before the end of the list, then all remaining possibilities are negated. Predominately, this will only occur when dealing with tanks, although there are certain debuffs in the game that can cause an the same result (such as the Choking Gas Bombs during the Professor Putricide encounter). There is also a phenomenon known as the crit cap, which will be discussed later.

Chance to miss

Every attack made has a certain chance to miss the target. This chance isn't directly related to level, but rather is a check against the attack skill of the player/mob and the defense skill of the player/mob. Although you will have a higher chance to miss against targets that are a higher level than you, it is because all mobs innately have all of their "skills" maxed and each new level raises the cap of each skill. There are four different formulae for determining your base chance to miss a target, depending on the target that you are attacking and the weapon style that you are using. If the difference between your weapon skill and the target's defense skill is equal to or less than 10 (mobs two levels higher than you or less,) then your base chance to miss will be as follows:

Two-handed/single weapon - 5% + (Defense Skill - Weapon Skill) * 0.1% Dual-wielding - 24% + (Defense Skill - Weapon Skill) * 0.1%

If the difference between your weapon skill and the target's defense skill is greater than 10 (mobs three levels higher than you or more), then your base chance to miss will be as follows:

Two-handed/single weapon - 6% + (Defense Skill - Weapon Skill -10) * 0.4%
Dual-wielding - 25% + (Defense Skill - Weapon Skill -10) * 0.4%

Using these formula, you would get the following results for the base miss chance of a level 80 character attacking with a weapon that has 400 weapon skill:

Level	Two-handed/single weapon	Dual-wielding
80	5%	24%
81	5.5%	24.5%
82	6%	25%
83	8%	27%

Chance to dodge, parry, block and glancing blows

The exact chance that a boss has to dodge, parry or block any given attack isn't precisely known, and it is quite possible that the values actually vary form mob to mob. For all practical purposes, it has been determined that a majority of boss mobs have a 14% chance to parry attacks and 6.5% chance to dodge or block attacks. You can use Expertise Rating, not Hit Rating, to reduce a target's chance to parry or dodge attacks. Again, Hit Rating will have no effect on a target's ability to dodge, block or parry attacks.

Glancing blows have been a spot of contention from patch to patch for a very long time running. The last officially confirmed calculations for determining glance blows is this:

10 + Defense Skill - Weapon Skill

This was introduced back in patch 2.1. Using this model, a player would have a 25% chance to land a glancing blow against a raid boss. However, since patch 3.0, a vast majority of parses have placed the chance to land a glancing blow as being 24%. It is possible that the formula has been slightly changed since patch 2.1, but we cannot know for certain. When doing any form of theorycrafting, 24% chance of landing a glancing blow is the currently accepted figure.

When you land a glancing blow, it will deal 30% less damage than normal against a raid-level mob, with the damage reduction being reduced by 10% for every level closer to yours the target is. You can only land glancing blows against targets that are equal to or greater than your own level, and there is no way to reduce either the chance to land a glancing blow nor the damage penalty. Note that you cannot land a glancing blow against another player, only against NPCs.

The single roll system and the crit cap

With all of the numerical bits out of the way, let's take a quick look at how the attack table actually works in real terms. For these examples, we'll use Mutter, the level 80 frost death knight (seriously, it's a real character!). Now, Mutter has chosen to run into ICC without a single clue as to what he's doing. He doesn't have any hit rating on his gear, he has no expertise and he didn't take key talents such as Nerves of Cold Steel nor Tundra Stalker. (Yes, he is exceptionally fail.) Mutter wants to feel like a berserking warrior of death and is wildly swinging at the boss from the front instead of being behind it, like a sensible player. One saving grace that Mutter does have is that his chance to crit is up to 40% by this point. Due to dual-wielding, Mutter has a base chance of 27% to miss with every swing. The boss has a 14% chance to parry every attack and a 6.5% chance to either dodge or block it. There is also a baseline 24% chance that all of the death knight's attacks will land a glancing blow.

Result	Chance	Roll
Miss	27%	0.01 - 27
Dodge	6.5%	27.01 - 33.5
Parry	14%	33.51 - 47.5
Glancing Blow	24%	47.51 - 71.5
Block	6.5%	71.51 - 78
Critical Hit	22%	78.01 - 100
Hit	N/A	N/A

As you can see from the table to the right, things are not looking too good for our death knight champion. In total, there is a 47.5% chance that Mutter's attack is going to fail to connect to the boss for one reason or another. After that, there is a 30.5% chance the each attack will deal reduced damage, leaving only a 22% chance that Mutter will land a critical blow against the mob. Notice that it is currently not possible for Mutter to land a normal hit using this attack table. This is because the roll caps out at 100% with all following resultants being "lost" or pushed off the table. This is an example of the crit cap. The crit cap occurs when a character has enough combined total results so that a normal hit can never land, and thus every attack that does land is either going to be a glancing blow or a critical hit.

One of the most interesting aspects of the single roll system, the crit cap wasn't a concept that had much theoretical application until Wrath of the Lich King. Up until this point in the game, it wasn't really possible for melee attacks to reach the crit cap outside of extreme circumstances. The thing about the crit cap is that it is a bit awkward in practice. First and foremost, hit and expertise rating do not have any impact on your chance to crit until you reach the crit cap. In the above example, Mutter's crit chance is artificially deflated because he has stacked crit at the expense of everything else. If he were to get 18% chance to hit, then he would end up with a 9% chance to miss and a 40% chance to crit. However, any additional hit or expertise he gained beyond that point would merely convert all of the remaining attacks into hits. Since everything things except glancing blows can be removed from the table, the crit cap is effectively 80.8%. If at any point you end up having a higher chance to crit than can fit on the table, then increasing your crit chance will have no net effect on your actual crit rate; you will have to gain additional hit or expertise instead.

For dual-wielding classes, the formula for determining your current crit cap is:

104.8% - (24% + (27% - Hit Chance) + (6.5% - Dodge Reduction))

For classes that use a two-handed weapon or a single weapon, the formula for determining your current crit cap is:

104.8% - (24% + (8% - Hit Chance) + (6.5 - Dodge Reduction))

A final note about the crit crap is on a different phenomenon known of "crit depression." Crit depression is an occurrence that happens against raid-level mobs wherein your actual crit chance is statistically lower than expected beyond the elements of RNG. It was determined through various parsing and testing methods that all melee attacks suffered a 4.8% crit depression, where the actual chance to crit against a raid boss was going to be a RNG variable closer to a value that was 4.8% less than the crit chance displayed on your character sheet. Due to the lowered chance to crit against these mobs, a player's crit cap is always going to be set against a constant of 104.8% instead of merely 100% since the additional loss of crit needs to be made up as well in order to push regular hits off the table.

Special attacks and the two-roll system

Everything explained thus far has been in relation to "white" or auto-attacks. "Yellow" or special attacks follow a different roll system than auto-attacks do. Special attacks are any attacks which are a result of a player's actively using an ability. This can be an instant swing ability such as Shred or Lava Lash or it can be an on-next-swing attack such as Heroic Strike or Rune Strike. All of these attacks follow a two-roll system instead of the one-roll system that standard attacks utilize. Beyond the difference in roll systems, there are two differences in the way that special attacks functions as opposed to normal attacks. First, all special attacks follow the same base miss chance rules as a two-handed or single weapon even when dual-wielding. Second, special attacks cannot land as a glancing blow.

A two-roll system operates in a functionally similar way to a single-roll system; there are just a few minor differences. When a special attack is made, the server rolls a single "dice" first to resolve how the attack lands. The first roll that is made determines whether the attack misses, is dodged, blocked, parried or lands normally. After that roll is completed, a second roll is made to determine whether the attack lands as a critical hit or a normal hit. To this end, the crit cap for special attacks is different than that of normal attacks. Instead of capping at 71.2% as with white attacks, special attacks have a crit cap of 95.2%.

Another difference between the two-roll system of special attacks and the single-roll system of normal attacks is that results from different tables are not mutually exclusive. This means that even if a special attack is blocked, it is still capable of landing as a critical hit. Obviously, however, critical attacks are still exclusive against misses, dodges and parries.