I think Harvey Dent's "change" makes some sens but, really, needed some more pushing.
I do agree that it was too rushed. As I suggested, my analysis was based on hints and clues picked up over repeated viewings. But you shouldn't have to watch a movie a few times to make sense of a major character's development.
The biggest criticism I would level at The Dark Knight
is that it was a quart squeezed into a pint-pot. Nolan tried to do too much in too little time. The pacing was positively breathless at times.