Haffner isn't Red John. Red John is smart. Haffner is an idiot, he gives a hint to Teresa that he's got an arachnophobia (hate spiders), he is connected to the Visualize and Jane and Lisbon know that.
Red John is Michael Kirkland. This theory is plausbile, the other theories are poor and boring for Red John.

Red John is smart likes Moriarty or Jigsaw.