Amen for healers. The warlock who poasted this is a jerk. As a healer, who has to drink between fights: if I'm sitting and drinking, to get mana, and you life tap you will get no heals. If I'm spending my time and vitrual gold to get mana back, you can sit your cheap, lazy ass down and do the same. Healers are not your personal mana battery. If you actually have to sit and drink between fights, too bad. All the other caster classes have to drink mana, too. Groups are NOT solo. You are now acting as a cooperative, not a single person who is pulling mutiple mobs as fast as you can to level. It is NOT ok do go into fights with half health, cause your pet will tank the mobs. Healers want to take every advantage they can get going into fights, and that menas full health for everyone. Your life tap annoys the living crap out of us. Just sit and drink. Or even better, tap once, and sit and eat and drink, so you get health and mana regen at the same time.
That being said, in raids where you run low on mana, sure, you can get health back. But be sure you are close enough to someone taking damage to get healing splash. Healers notice who takes damage, and who takes damage often. Those are the first to be ignored for heals in a tight situation. In the long run, they are not worth spending mana on to keep up. Constant use of life tap will put you on that list very fast. You become as bad as the loser that always stands in the fire. If you life tap at the wrong time, we let you die first.
Keep in mind, healers cannot kill you. But if you are stupid and take unnecessary damage, we can let the Darwinian process finish its work.