To be honest, my first thought when my health bar gets low isn't "Oh good, Defiance will kick in now," it's "Holy crap, do I have any heal inspirations?" or "FLY AWAY!!!"
There are simply too many mobs I face right now (doing a lot of Tsoo and BP missions) that can stun or sleep or hold me, and Defiance doesn't do a thing when you can't take any actions and an Ink Man is wailing away on you. I'm better off bailing or popping an inspiration than waiting for more damage to kick in -- it's the damage I'm taking that's the problem, not the damage I'm giving out.
