I was in a group where someone said this. I find it funny, because if a mob is on you you're "tanking" it. Just because you may be ill-equipped for it doesn't mean for a brief moment you're weren't performing the role.
I think quite often people forget how hard things hit because they aren't usually the ones getting hit.
I secretly like when someone pulls something off one of my tanks and summarily see their health drop. The player usually watches their aggro the rest of the run.
1 day ago