@Meddler: What are your thoughts on an equivalent of "Minus Strike"?

For context, see the above.

Basically, it'd be a skill that causes your next basic attack to deal bonus damage that gets stronger based on your missing health (not the enemy's). If you're healthy, the damage is okay, but if you're almost dead, it does TONS OF DAMAGE.

Very clear strengths, pretty clear play, etc. It'd be an awesome skill for a Dark Knight Champion.

Yay or nay?