I'm sick of warlocks who are affliction who don't lifetap properly during boss fights.
Yes, its your job to DPS, its also your job to lessen the stress upon healers.
So, I hear you asking already... when do I lifetap Mister Abs?
The answer is: You clip Haunt, and lifetap immediately after you finish casting Haunt. You see, Haunt is NOT a DOT. Its an instant damage spell followed by a 12 second debuff. When you clip it, your little healing ghost starts flying back to you. If you lifetap before that ghost gets back to you, it will heal you up almost to full.
So please, do your healers a favor on boss fights, and use this trick. No lifetapping 3 times and going down to 20% health crap.