All classes and specs in game have always had a stat they had to stack to achieve their maximum dps. For most classes it now is their primary stat above all, being hit-capped and then usually there is one rating sticking out above the others. For retribution paladins it’s strength and then mastery, for enhancement shamans it’s agility and then mastery and the same holds true for many other classes. But what about tanks? Do they have a priority like that as well?
I’d actually say we do, but with a few annotations. Whereas our primary stat, stamina, is really solid, we don’t “have” to reach specific caps. Stamina is, just like for a dps classes our main stat. That is, until we reach a critical point where healers have enough time to keep us alive. After that, things become interesting. When you don’t need more life to stay alive, you focus on taking less damage. But how to do this. One way to do this is making sure you avoid hits completely, which can be achieved by both dodging and parrying. The other way for both shield wearing classes is to get more mastery, which only reduce the damage taken by a set amount when they block.
Now you might be thinking that taking no damage is better than taking less damage. Whereas I normally would agree, this isn’t the case with taking. The thing with mastery is that it reduces the damage you take more often than the amount of times you completely avoid an attack. For protection warriors, their mastery increases the chance for them to block 30% of an incoming melee attack and gives them a chance to critical block for double of that. With paladins, their mastery does also provide block, but whereas they can’t critical block, they gain it at a much faster rate.
The goal for tanks in the current content, and has been in previous content as well, is to take as little damage as possible AND make the damage you do take predictable. Being predictable makes it easier for your healers to keep you alive, and saves their mana, because you make sure there is less chance of a couple of big hits in a row.
So, as stated before, our goal is a predictable damage income and the best way to do that is to make sure all damage you take is the same. We do this by gearing to be “unhittable”. Unhittable is basically making sure there is never a full hit going through: everything is either parried, dodge, blocked or missed. By doing this you never take the big hits, but multiple smaller ones. And this is where mastery comes in play. While dodge and parry are affected by diminishing returns, mastery is not and it quickly allows us to get to that unhittable cap. And then, when you are at that unhittable cap, you basically reduce every melee swing with 30%. How awesome is that? Wouldn’t you just love to have the certainty that you always take 30% less damage than what the boss was planning to hit you for?