Originally Posted by
Maveaux
Progression tanking is all about consistency tho. That's the exact reason why top tanks always choose the consistent path, even tho the other one may be better. Take DKs for example. Mastery and avoidance are equal in terms of mitigation, but avoidance also lowers mana cost. Yet every top DK chooses mastery, because avoidance is RNG.
And why is RNG bad? Imagine you are below 30% health. Imagine you are raiding heroic mode progression and the boss can and will kill you in two swings. Imagine you miss 3 times a row just then with a skill that could save your life. You just wiped the raid, pretty much. And if you are below 10% health, even a single miss can do it for you. And if you are seriously raiding heroic progresion, you will be in that situation very often.
As a tank consistency is always better than the overall performance, at least in progression where this stuff actually matters.