For all melee classes, being over the Critical Cap is the situation where a portion of the player’s critical strike chance does not benefit a part or the whole of their DPS.

Melee attack types
There are 2 kinds of melee DPS: white auto-attacks and yellow special attacks. When talking about the Crit Cap only white auto-attacks are relevant.

White auto-attacks are affected by the following factors:

    Glancing blows: This happens due to the level difference between the player and the Boss. As a Boss is always considered a minimum of 3 levels above the player, all of the player’s white melee attacks will have a 24% chance of being a Glancing Blow. Which is a reduced damage white attack that is unable to crit.
    Dodge: When a melee attack happens on a Boss, there is a default 6.5% chance it will get dodged, and obviously a dodge cannot be a critical strike. This can be lowered and be completely negated with the use of Expertise rating and talents.
    Parry: Attacking from the front of the Boss causes this and results in parries, failed attacks that cannot crit. Eliminated by attacking from behind.
    Chance to miss: The white attack’s chance to miss for a dual-wielding Enhancement shaman is 27%, which goes to 21% when choosing Enhancement spec, thanks to Dual-wield Specialization. The remaining 21% can be reduced and totally nullified by the use of Hit Rating. Misses can’t crit either. Really!
    Crit Depression: On a Boss-type mob, the ratio of white critical strikes will always be 4.8% lower than what is presented on the Character Sheet . What does this mean for the player? Just that they need 4.8% more crit in their char sheet in order to be doing the desired Critical strikes on the Boss. Earlier tests have claimed there is also a limit to the white-attacks that can be converted to Crits. This is not the case, there is no such limit, all normal white-attacks (not glancing blows) can be converted into critical strikes.

These factors can be unified into a single formula, like this:

Maximum Critical Chance (MCC) = 100% - (Glancing blows chance) – (Chance to be Dodged) - (Chance to be Parried) – (Chance to Miss)

This MCC number is the point where all white melee hits have been been removed from the table. Meaning that all melee attacks will be either glancing blows, dodges, parries, misses or critical strikes. At that point one can only increase their ratio of critical strikes by either adding more Expertise or more Hit rating and only if those are not capped already.

However there is still Crit Depression to take into account when attacking a Boss. So in order to reach the true MCC level on a Boss, one would need 4.8% more crit then is shown on their character sheet. For example, if your current MCC value is 70%, you could only remove all white hits from the table by having 74.8% on your character sheet. That point is also referred to as being Crit Capped as any additional Crit Rating past that point will have no effect on the ratio of critical strikes.

Crit Cap= MCC + 4.8%