Miss

A miss is a failed attack, it deals no damage. As well as foils any other mechanic that may have resulted from a successful attack.

 

See also: Combat and Combat rating system

Base Miss Rate

The Base Miss Rate for White Attacks, is calculated through the difference between the attacker’s Attack Rating and the defender’s Defense. Which is 5% if the Attack Rating is equal to the Defense Skill. If a player is Dual Wielding, they inherit an additional 19% miss chance. It is currently untested if a dual wielding mob incurs this penalty.

The Base Miss Rate for Yellow Attacks is at a maximum 5%, unless a debuff is applied the attacker that increases miss rate. The Dual Wield Penalty does not effect the miss rate for yellow attacks.

Player/Mob vs Player

When a player or mob attacks a player, the base miss rate is 5%.
For each point of the defender's defense skill over the attacker's attack rating, the base miss rate increases by 0.04%.
For each point of the attacker's attack rating over the defender's defense skill, the base miss rate decreases by 0.02%.

Player vs Mob

In PvE (at least), a player's chance to miss is determined solely by the difference in the defending mob's Defense Skill and the player's Weapon Skill. Further, the effect is not linear. So, there are actually two different formulas that might apply, depending upon whether the difference between the mob's Defense Skill and your Weapon Skill is greater than 10 or not. Here are the two formulas:

   * If the difference between the mob's Defense Skill and your Weapon Skill is less than or equal to 10 then the formula for calculating your base miss rate against that mob is: 5% + (Defense Skill - Weapon Skill)*.1% 

   * If the difference between the mob's Defense Skill and your Weapon Skill is greater than 10, then the formula for calculating your base miss rate against that mob is: 7% + (Defense Skill - Weapon Skill - 10)*.4% 

Applying these formulas gives the following base miss rate for a Level 70 character with a 350 Weapon Skill:

   * v. Level 70 mob: 5.0%
   * v. Level 71 mob: 5.5%
   * v. Level 72 mob: 6.0%
   * v. Level 73 mob: 9.0% 

Thus if you are a Level 70 character with a Weapon Skill of 350, you need a Hit Rating of 142 (9.00%) to never miss a shot against a Level 73 boss (or skull mob).

What this means is that there is a big +hit benefit to keeping your Weapon Skill within 10 levels of the mobs you are trying to fight. For example, by improving your Weapon Skill from 350 to 355, you effectively reduce your chance to miss against Level 73 mobs by 3%! However, after getting to 355, increasing your Weapon Skill the next 5 levels, to 360, only reduces your chance to miss by an additional.5% (or 3.5% in total). Also, note that there is a huge jump in miss rate reduction by going from 354 to 355 Weapon Skill. This is the point where you switch from one formula to the other, and so this particular single point of Weapon Skill is worth a dramatic +1.4% hit against a Level 73 mob/boss.

Racial Bonuses that provide +Weapon Skill thus turn out to be pretty valuable for improving your +hit capability. For Humans, Dwarves, Orcs and Trolls their racial bonuses increase their Weapon Skill at Level 70 from 350 to 355. With a 355 Weapon Skill, your base miss rate against a Level 73 mob (or skull boss) is only 6% instead of 9%.

Also, in applying these miss rate formulas, fractional Weapon Skill levels are dropped, not rounded. So, say you have are a Level 70 character, and you equip a piece of gear that gives +15 Mace Skill Rating. In theory, this equates to 3.8 +Weapon Skill Level. And, in theory, Blizzard could have used the fractional .8 in its subsequent calculations of hit and miss, or, perhaps, rounded it to 4.0. But it doesn’t work that way. Instead, the fractional .8 Weapon Skill is simply dropped altogether. You get 353 Weapon Skill for purposes of all hit and miss calculations.

Level is not a factor except when attacking a mob level 9 or lower.
Miss chance against a low-level mob is a percentage of normal equal to the mob’s level divided by 10.

Calculating a mob's Defense Skill or Attack Rating

This is a rather simple formula. It is the Mob's level multiplied by 5.
For Skull Bosses, the formula is your level plus 3, multiplied by 5.