Do you have any medical evidence to back this up, other than what the ME has said may have happened?
I've already given accounts here of people attempting to commit suicide via gun that only successfully damage their frontal lobe and subsequently have to fire a second shot to end their lives.
The frontal cortex is mainly responsible for emotions, impulses, and rationality. If he remained conscious, he probably would have been disoriented, not quite sure what was happening, and probably almost in a drugged state. I think that would explain the lack of defensive wounds.
As I've stated before, it seems likely that he was shot in the bathroom and the blood around the sink is from him either kneeling or standing over it, dazed. He probably stumbled around, where Arias met him in the hallway with the knife (and where the vast majority of blood was on the carpet). That is the only way I've been able to make the sequence of events fit together as we know them.