The bare minimum I expect from the roles:

Tanks: Use cooldowns and just position enemies so they won't hit allies.
Healers: Heal the party when needed and do damage when it's not needed.
DPS: Do decent damage.

That's all I expect, and the amount of times that isn't even met is fairly high. That btw, is different from the bare minimum I expect from just playing the game. The bare minimum there being don't double stack stack markers, don't run away from the group with them, keep the flare/aoe markers from other people, and actively TRY to dodge AoEs.