I actually tossed around the idea of a healing class that primarily healed through their own health pool. I didn't associate it with necromancers (though that could certainly work) I even had a very similar idea to the link, except I think I was thinking of having the necromancer link their health pool to someone else.
Originally Posted by BruisedOoze
Such a class could regen their resource (hp) through dots and attacks which leeched health from the enemy (use for mana). Their damage could be weak, the heals would probably have to be multiplied, but that might go along the lines of what you were thinking.
Of course, if it were to follow the DK hero class model each tree would need to be viable for healing and DPS.
So you could have one tree as a self-sacrifical healer, one where they might use minions to heal, and then I don't know what the third would be. And, of course, all of those trees would be plenty capable as DPS.