Is There a Mastery Cap?

One topic I have been asked about several times since patch 4.0 is Mastery.  Specifically, players (especially assassination rogues) are told that they should reforge to mastery, and so they want to know if there is a cap.

The answer is:

1. It will vary depending on the mastery that is specific to your spec
2. You have no chance to reach that cap currently so don’t worry about it

Now that the basics are presented, here are the specifics for rogues…

Assassination

Mastery is Potent Poisons.  It gives a 28% increase in poison damage, plus an additional 3.5% per point of mastery.  There is no apparent cap on this.  If you somehow got your mastery beyond 100%, that’s just more damage.

Combat

Mastery is Main Gauche.  It gives a 16% chance to proc an extra off-hand attack, plus 2% per point of mastery.  This has a cap that you would reach if the chance to proc the off-hand attack reaches 100%.  When that happens, the extra attack will happen every time, and any additional mastery will not gain anything.

At 2% per point of mastery you would need 42 points of mastery to reach that cap.  The conversion at level 85 is 179.28 mastery rating = 1 point of mastery.  Therefore, to have 42 points of mastery you would need to have 7530 mastery rating to cap.

Subtlety

Mastery is Executioner, which increases all damage by finishing moves (and the attack speed bonus of SnD) by 16%, plus 2% per point of mastery.  Like assassination, this is a straight damage increase and as such it should have no cap.  You can exceed 100% on this and it only means a bigger increase.

I suppose its possible that there is some additional mechanism in the mastery system that has not been revealed that would change these calculations.  At the moment, there is no need to worry about a mastery cap.