And you don't even mention the fact that the Joker already busted out of jail and half-expected his re-arrest. His plans for escape might be endless.

Let me tell you, the two main objections you raise are the same main reasons I don't readily list TDK as my favorite superhero movie. (The other reason that comes to mind is contrivedness, but that's almost inevitable for a philosopher-artist.) But what did you think of the movie before the last five minutes?