Warrior Q&A:(
Source)
But only 9 for your specific character, and only three for your specific spec. Mastery is simply a way to make a given talent tree give you the kind of raw stat bonuses you'd want without having to blow points on talents to get it. It is my understanding that as you level, your Mastery stats will increase for whichever talent tree you are spec'd into.
And then on top of that, you can find equipment with the Mastery stat on it that increase those three specific attributes. So maybe your mastery tree gives you +Hit and you're hit capped; you can pass on Mastery, in that case, in favor of something else.
The problem is, the third mastery bonus looks like it will be this awesome effect you always want (like an extra chance to hit or a HoT effect for every spell you cast)... the question is, will WoW-players (usually focused on stats) suddenly take their eyes off the numbers and consider whether improving a given
mechanic is worth it.
In other words, WoW is movingtowards more interesting gameplay choices than "+1 AGL vs. +2 AP -1 STR". At least that's how I read it, but I could very well be wrong. Still very early and we don't really know shit, and what we do know is subject to change at any time.
After all, Spirit Link, PW: Barrier and Heroic Leap have all been in the Beta before... They didn't make it in last time, so... I'm just saying, nothing is set in stone.