Maybe his tank smells funny and he just wants to get away from him? On a more serious note, no idea what's wrong. The wards got nerfed big time from release (maybe it's just the 20+% buff, not sure, but the rep got nerfed, so...). Where we had trouble with 2 healers at the beginning it's now no problem at all to do it with one healer. I don't move my DPS too far away from him either. I just spank him with my pally for 2 seconds and go all out with the nukes. We are doing this with just 6, tank, healer, 4 casters.