Yes we do tend to do damage and wake up sleepers but you have to understand that as a tank we are focused on getting has much agro as possible and facing the enemy away from the party as best we can. While you know what mob you put to sleep the only indication we have is tinny little purple things coming off their head and most of the time with all the spells and junk going off we can not see that at all. The solution is not that the tank should be on the lookout for sleepers as that is not our job. The solution is you should mark your sleepers so we know to leave them out of our agro rotation. Or if you are just to lazy to mark yourself you can ask the tank to mark them before he pulls. I do this all the time. Expecting the tank to know who you put to sleep without telling him in some way is just stupid.