I'm okay with awful tanks, makes me look like a god in comparison!
On a serious note, I just don't know. I didn't know how bad some tanks were until I started healing - and as a Dark Knight, there is nothing worse than seeing DKs not using grit / darkside on dungeon runs, or just ignoring their buffs. It's all a matter of opinion and choice I realize that, but I really think it's better that they tank and let the healer dps when there are windows rather than pretending they are a dps class...