So, at first I had a similar issue with getting only the dominate animation with the Punchshrimp boss. But then instead of walking into the boss (from either side) after getting it dazed. I was able to Power Punch and get the submissive animation.
I guess the only thing that's on my mind is implementing something to indicate when your close enough to Power Punch a dazed boss, like a flashing outline around the boss? Just a thought; otherwise I'm enjoying my time playing.