I have presented a kinda non-theory here http://www.whoisredjohn.com/See-a-theory-Red-John/6920 to make it easier to dismiss Haffner, but the thing that bothers me is that Heller said RJ is someone who was there from the beginning. Now...he couldn't have known from the beginning that the show would last 4-5-6 seasons, so he HAD to have someone lined up to close with, just in case the show would last say 1 or 2 seasons. So I guess that would leave only McAllister or Partrige right?
For the record, my brother thinks Red John is Patrick Jane, and it did seem plausible, until I read some of the the other "theorists" feedback. Originally, I thought Red John was the red headed spiritual advisor, but I now move my theory to Grace van Pelt. She acts too innocent- and as Johnn Depp would say - "Evil wears many masks, but none so dangerous as the mask of virtue." She's always around, so sweet, has red hair, and she knows where Patrick Jane is on the Red John investigation. She would have the "last laugh", if it's not Patrick Jane. I have nothing to base it on, really, except gut. I haven't rewatched any of the episodes. But, I welcome feedback and if anyone can prove / disprove my theory let me know.