Krauser is a tough opponent, trust me, in Professional mode I hit him directly with the Infinite rocket launcher while he had his shield arm up and he deflected it!
I was shocked because in norm that metal shield didn't protect him from it. I blasted him and he like, hit me and killed me, but i digress.
Aim for his right leg, its just beyond the protection of his wing shield. Once hit enough he will crouch down and retract his arm sheild, at which point you should unleash heck on his exposed cranium. Good luck. The tmp is best for trying to hit his unprotected leg, and remember to try to keep your distance and if ur prompted to use the dodge combo, keep ur fingers ready because they tend to stack up.
Conquering the world, one step at a time.