I now believe I may have also found some evidence for this theory. If you look at TDKR, a good chunk of the story is copied and pasted content from books like No Man's Land, Knightfall, The Dark Knight Returns, and Cataclysm. While BB and TDK were also inspired by many Batman stories and had a couple of scenes here and there that you can consider straight from a Batman comic, the movies were their own stories at the end of the day. TDKR is without a doubt the movie with the most story influence from the comics out of the trilogy and I would say that about half or more of the plot in the film is plot from the comics. This isn't really a bad thing but I think it shows that Nolan either could not come up with a story for the third movie (once again, he couldn't use the one he originally had in mind because he didn't want to recast the Joker), lost the passion to come up with a complete solid story due to Ledger's death, or both.