All life as we currently understand it is water-based.
Think of it as desiccation on steroids.
I'm not saying it's a perfect solution (so to speak!
) but to say it doesn't work because isn't thematic is simply wrong.
One might just as well argue that non-vampiric undead should be immune to reinvigoration of any kind.
The point is path and nation balance.
Drain Life is the closest thing to a sure single target killer in the game.
The three big water nations (atlantis Ryleh and TienChi) are all conspicuously underutilized, death/ermor is not.
Rabe the Naturalist