You could summon Skeletons in DOS1 out of nowhere, why should you now need a corpse? Does not make much sense in my eyes.
Sorry, my bad. I meant: Heals for 75% of current life if you sacrifice 50% of your current life. Or perhaps better: Heal 4 turns for 25% of current life, but sacrifices 50% of current life. (Of course can't be cast on yourself.)
Honestly I'm not sure if not even then just learning Restoration for one point into Water would be more attractive. Probably would need also some kind of buff for the target or the caster?
Lhose restoration might restore less at once, but the restoration restore life for 3 turns if I'm not mistaken.