I know how to beat Devan pretty easily: I just buttstomp him. When you shoot him his power goes up sometimes. The first time I played the dragon Devan part, I had to shoot him a lot, but now, when I shoot him once with my blaster, he falls down. It's pretty weird. I had a hard time beating the Bilsy Boss. It's because he can teleport, and his fire balls can get you mostly from anywhere.