They did, in fact, "enhance" the voice in post for many scenes. Generally I didn't mind the voice at all and think it makes perfect sense. However, the monologue at the end I didn't hear too well in the theater. The music was swelling up so much and his voice was so distorted I couldn't make a lot of it out. I thought it might of been the theater I was at, but I guess not.
I think the Joker should have killed Gordon's son. Then
I think the film would have had the balls many people claim it has.