If this film is set in the complete plausible, then eplain The Joker. He may look like a real person, he may have the same desires and perform similar actions that a serial killer could possibly perform in our world, but that doesn't exclude The Joker's supernatural abilities.
The character plans with such intricacy and precision, knowing certain actions and decisions are going to be made before they happen, knowing exactly what Gordon, Batman, and Dent are planning to do. The Joker is practically an omniscient character. He reminds me of/inspired Hannibal Lector, another character that has supreme intelligence, a master of manipulation, abilities beyond what any normal human being are capable of possessing.
Yet, like Lector, The Joker exists in a world that looks like ours and at times can feels like ours. But the fact that these characters, with their superhuman mental capabilities, exist in their respected worlds, it immediately calls the plausibility (in relation to our world) of this world into question. What kind of worlds allow for characters with this type of knowledge?
It may not be as glaring as a monster made out of clay, but it has to be recognized. Something like this clearly sets the Nolanverse apart from our world, no matter how much they may resemble each other, and definitely offers up fewer limitations than what some people originally thought of the Nolanverse.