What i do not get of your story is if he actually sleeped the target he knocked back?

If he actually did sleep them, remember:
- Sleeped targets do not build aggro. If you were on top of the list before sleep, you will still be when it wakes up.
- Dots that have been applied in advance will keep damaging the sleeped target and will not wake it up.

From what I understand it sounds like you overreacted a bit, could have finished the dungeon without major problems or could you not?