I have a feeling that it's Haffner. When Cho was speaking to the private detective who attempted to bug their office, it was never confirmed that she actually worked for Red John or Visualize. Even though she agreed with Cho, he mentioned it first and she could have just said yes to avoid being arrested.
Why, after all this time, would Red John resort to such depths in order to get information about the team? The three dot tattoo is a symbol of the tiger tiger group, but not necessarily Red John. Tiger Tiger has an, as of yet, unspecified agenda, but one that is very different to Red John's. Red John is definitely aware of the group, and may be a member (or former member). He covered very easily have covered up his tattoo with make-up.
With regards to the other suspects, Bertram is too tall and is bald (unless he wore a wig when he was with Rosalind Harker). Brett Stiles is too old, but definitely has some connection to Red John (maybe he inducted him into Visualize). McAllister is the right age, but unless he's a REALLY good actor, doesn't have the charm necessary to convert people into disciples. FBI Smith is a bit too rotund and even though he has a fear of heights, the therapists recording states that she wasn't sure if this was actually real or not. This could be a misdirect on behalf of the writers.
Haffner is the right age, height, build and you can definitely see him being charming when he wanted to be. He is a member of Visualize and has been ever since he was a teenager when he was a maladjusted and distressed boy. He insists that the cult helped him. This could indicate that he was part of the Visualize farm project that had that barn. In addition, it's entirely possible that Jane's carnival came to town and that the two of them met, albeit very briefly, when they were kids.
He is formerly an FBI agent in the Organized Crime Division, and is an expert in wiretaps and creative surveillance techniques. So he could easily have used those skills to keep tabs on Jane and figure out the likeliest people Jane would create as a list of suspects.
It is clear that he has a soft spot for Lisbon, which would explain why RJ didn't kill Lisbon at the same time he killed Brett Partridge. Also, Haffner met PJ a long time before Jane met Lorilei. The definitely shook hands and you could see that, initially, Haffner wants to work with Jane and have a positive relationship with him.
Given his connections with CBI, FBI and whoever else his clients are in private security, he definitely would have become aware of the Tiger Tiger group. I'm trying to figure out why he would make Jane aware of this though. Maybe he knew that this group had Jane under surveillance and by helping Jane expose the group he was helping himself (as if the group became aware of RJ's identity through Jane he would be unable to continue killing).
The promo for The Great Red Dragon shows a mass of SWAT team officers surrounding a house and Jane stating that Red John is one of them. Whoever's house it is, obviously has dressed as a Swat team officer in order to hide in plain sight before making his escape. Haffner is the only one of the suspects who would have the knowledge to successfully act like a Swat team member without drawing attention to himself.
