I remember noticing a while back that Nova Bomb was largely useless in PvE outside of the T1 enemies. I didn't think it should nuke a boss, but should do more than it does. It's one of the reasons why, a while back, I temporarily switched to Sunsinger. I felt that the periodic extra armor or faster-whatever and spamming grenades was probably more useful in a pinch. I've gone back and forth a number of times since.