I'm thinking of denying Gravity units that kind of delicacy in the first place (that is, do not let Gravity units be targeted with this) ... but outside of Gravity, there's still the Voodoo Doll (0/16), Golden Dragon (10/10), and Stone Dragon (8/10) to think about. And we're not into upped territory yet.
Also, if you worry that most decks that use this would be Grav-based decks that splashes Life instead of Life-based decks that splashes Grav, just raise the casting cost.