Well at least we have a good reason for losing health; our mana (and probably all means of replenishing it) are gone, so we are going for our reserve. It's different with all the warlocks who lifetap almost to death and then stand looking impatiently at the healers (who are drinking like the rest of the normal casters).

That's the difference between a good lock and a bad lock: good locks are happiest with a single (one) HoT on them or while standing next to a lightwell. They NEVER run out of mana, because they're keeping their spellpower up with the glyph of life tap, and either:

A) Use the same amount of mana they tap into, or
B) Downrank Lifetap to accomodate the amount of mana they tap to.

A bad lock will wait until he or she has 20% or less mana, then tap to full... and either whine on vent/chat for heals, or die in a fire... and then whine/chat for grieving purposes.

Especially after raid wipes, it's evident. A good lock will summon his pet, activate armor, drop a soulwell, tap to full THEN USE A HEALTHSTONE. Then, grab another from the pot; if the HS doesn't heal them the full way, Fel Armor or magefood will. Bad Locks will summon pet, tap until full... and then sit.

mages can't use health to reup their mana pool... there is no convert x -> y component... therefore at the end of combat (if we live that long since healers are probably going to be busy keeping the party alive if we're already this mana taxed) we're going to have to sit and drink just like every other real casting class out there...