How should I trim this door?
I agree with Trevor on this statement of his - which was my thought before I read his answer.

"The ultimate solution would have been to bring it all forward so the door was registered to the wall with the light switch, and pad the post on the left to bring the corner out to match. "

After that then I would have simply used dry wall on the interior side of the bathroom to make it look like it was simply a reason for that floor plan - like maybe a pipe was there or the wall had a load bearing beam back there anything to keep it from standing out as an OOPS. 

Then it would be just as Trevor said the visual side that will be noticed looks like it should look, and the side that would need tidying up would be hidden for the most part.