If a tank is saving mitigations for bosses, he must not be wall pulling. If he knows enough to wall pull and still doesn't use cds, something is wrong because there's no way he's surviving much of that. If a tank single pulls and is never told differently, they may in fact save cds for bosses though, as that seems logical to a noob and the healer can easily mask how much damage they are taking. And mid level tanks casually playing the main story might not know how to play the role optimally, since ARR dungeons are so awkward to wall pull much of the time, fewer people are gonna tell them to do it until HW. It's not unreasonable to think a level 60 tank playing casually might not fully know these things. If they know all of this stuff and still don't do it, they're basically saying they're bad players without saying they're bad players.