They improve on Doc Ock in SM2. Recently Ock has depth in the comics but before SM2 Doc Ock was one note and uninteresting (but still my favourite Spidey villain, go figure).
Doc Ock has had depth for decades. Did you ever read Spider-Man Unlimited #3 back in the 1993 for example, where you saw his terrible childhood, his abusive parents, and how he once had a woman he loved but lost etc? It really drew on the parallel between him and Peter. He was a lonely science nerd, bullied and with no friends, unpopular with girls, grew up in middle class New York, acquired his powers through a science accident etc.
I know they made some changes to Doc Ock, but he was very faithful to the comics in many other areas:
http://molinaock.blogspot.ie/
The biggest problem for me in TDK is Two-Face, they establish Dent as the 'White Knight' a man who is not afraid to go to any lengths to ensure the safety of the city and the rounding up of criminals but all of that is gone when he loses half his face and girlfriend. Nope, not buying that quick a chance that comes out of left field, either Dent's whole persona was a lie or the character of Two-Face is completely unearned.
Oh come
on. He was horribly disfigured, betrayed, and the woman he loved was murdered, and you don't buy that he mentally snapped over that? There's people who have snapped for less than that in real life.
It wasn't a quick fix where he went crazy because of some green gas that turns you nuts like Green Goblin, or resurrected by cats like Catwoman in BR, or even something shallow like doing it because he felt cheated out of money.
He suffered real loss, and was left horribly mutilated. If that wouldn't damage someone's psyche then I don't know what would. It's better motivation than half of the comic book villains.
You even saw preludes to it when he kidnapped one of Joker's men in an ambulance, tied him up in a back alley and terrorized him with a gun. That was just because Rachel had been threatened. It's like if he could do that just because she was threatened then imagine what he would do if she was murdered.
I think Ledger is electric as Joker. Sure, the fact that an agent of chaos has the most well executed and elaborate plan ever doesn't make a lick of sense but I love the performance.
He was lying when he said he wasn't a schemer. Just like he was lying to Batman when he told him where Dent and Rachel were and he had to choose which one to save. Batman never had a choice. He was tricked. Same as how Joker lied when he told Dent that he had nothing to do with Rachel's death just because he was in jail at the time.
Joker is a liar and manipulator and says what ever he has to in order to get what he wants.