this is of course their primary role in m+. and this you can get a sense of by running the normal/heroic/m0 learning route.
i ran into something in this arena over yesterday in halls of atonement.
I don’t know if I was running a “popular” route, but I know that that the route I was doing would get the %.
the healer was a priest and he pulled me in the direction he wanted me to go, including pulling me such that the stonegargoyle’s frontal was pointed at the group. he was like “pull more it’s only a 7”. he told me to stop moving the first boss, which is the opposite thing to do. i have to move the boss becuase he drops puddles and we have the big cross we have to dodge. movement is required. then he demanded that I pull mobs into the third boss. we wiped. we get to the last boss, and everyone but me died so I wiped it. happened again. group votes to abandon (lol) and he types “Tank learn route”.
my route was fine, just not what he wanted and it was a painful run that didn’t even finish. not because of my route, but because the team didn’t know the mechanics of the fight.
i agree with this statement with the caveat that this issue is that you are learning on someone else’s key.
as noted above, not all keys win, but I think it unfair to a key holder for a tank to not know the content, or not feel confident with the content.
I think more people would be willing to tank if there were places like practice dungeons where you are all by yourself to experience the content, rather than just read about it, and there are no consequences to a key holder.
I understand the efficacy of this idea, but some people want to tank and not dps. “forcing” them into a different role to learn the role they really fit the bill, although I have done it.