I've played a bit with Defiance using both a lvl 45 ice/energy and a lvl 4 "sonic attacks"/energy. I will say that it added some motivation for me to hit another mob when normally I'd be resting.
Unfortunately, I don't feel like it addresses the core issue of why I lose a fight. I lose fights not (usually) because my tactics are bad, or because I underestimated my enemy, or because I'm not doing enough damage, but because I missed too many times.
I'd rather see Defiance be an Accuracy bonus that scales up a little more quickly than the current implementation.
