This might have already been asked, but...

Why DIDN'T Doey use that monster-ized form of his against the Prototype? I mean, it seemed powerful enough to the point that he could most likely take out The Prototype and the Doctor. Maybe, just maybe, I'm looking too far into this, or maybe I'm not looking far enough and I've missed things. But I really do feel horrible having to have killed him due to the fact that he was actually really nice, and was just going through it rough because he basically had 3 different personalities stuffed into his VERY BEING, and just now having to realize this OTHER method that could have worked.