If you actually tank, there's nothing wrong with that. It's working as intended.
But when you get a SCH in Doma Castle who never heals the tank at all and tries to let Selene handle the whole thing while they spam Broil? Soon as the tank dies more than once because of it, that's kind of a problem...
Or you get stuff in Sigmascape where only one healer is healing at all, and they're doing all the work because the other one apparently thinks they're playing a DPS class.