I understand. I was trying to reason a way that it should be negative health, without forcing it to be over-complicated purely for thematic reasons. I like the concept of negative health, although you make a good point with skeletons dying from it.
My thoughts;
thematically, this isn't just your average enchanted wad of bones (skeletons). This guy is a Necromancer. One who has power over the dead. Undead. He takes hate and destruction, and turns it into his power. A rain of fire is his best friend. His power grows as others die.
What he is truly afraid of, is not death, but life. Growth. Blessings are his curse (as in the card Blessing). Things that grow are his fear, and ultimately, his weakness.
mechanically, it is a unique way of adding a mix to creature control. Now your blessing or momentum or basilisk's blood can now take care of the enemy handily, as longs as its a Necromancer receiving the spell. Now what's Necromancer good for? Rage Potion anyone?