I would take a character driven piece over a bloody R any day of the week! I don't think we have to worry about TDK not being character driven with Nolan at the helm; it most definitely will be a smart, character driven movie. Don't forget, unlike Raimi, Singer, Del toro, Nolan writes and directs: So it's definitely going to be quality, otherwise nolan wouldn't have done it in the first place. Nolan doesn't care about money like the rest of these directors, he's just out to make a great, unique film.
And I don't think we have to worry about the lack of violence that the Joker will bring, either. I mean, it took the guy five minutes to kill four people (hint, hint, prologue..cough...um, yeah...) Killing two directly, and the others indirectly.