Just because your watching your hate, doesn't mean the dps aren't watching their's. It's very possible that the dps wanted to AOE or simple do more damage and couldn't because you weren't generating enough enmity, so they had to gimp their own damage, all the while you think you are generating enough emnity. I have had this happen many times before where I end having to cast and damage and rotate between all the mobs because a tank wasn't going to be keeping hate if I kept attacking the same one. The mob never left the tank, and he never lost agro either, because I paid attention to my hate. I'm not saying your at fault, however there is another side to the story and we really can't give you an answer with out. Most healers will put DoT's on adds, as well as heal so they will be generating extra enmity, it's possible the healer wasn't able to do this.