Walter Mashburn=Robert "Bob" Kirkland=Red John
I feel that you have to take the entire series into consideration to find out who Red John really is.
Walter Mashburn always appeared strange and totally qualifies to be Red John, but in this text I wont focus on what makes him a Red John suspect, but rather how he can be the same person as Robert Kirkland.
For some reason Mashburn was completely removed from the series, about the same time that Patrick Jane killed "Red John" (Timothy Carter). I don't know if it's just me, but I can see strong resemblances between Walter Mashburn and Timothy Carter, which isn't strange since Timothy is trying to imitate Red John.
Walter Mashburn's latest appearance in the series was in the episode "Red Hot" (S03E07).
Robert Kirkland doesn't appear in the series until "Red Dawn" (S05E05), which means that Mashburn had more than enough time for plastic surgery (and more than enough money to afford it).
This could be the reason why Kirkland asked Jason Lennon if he recognized him before killing him.
Mashburn was a suspect on Jane's original suspect list (people he had shaked hands with), but he isn't on the latest list. Robert Kirkland is on the latest list, while he isn't on the first one. So, when Heller says Red John is definitely on the list, he isn't lying. His identity has just changed.
In the latest episode (S06E02) Rigsby checks the names of Sophie Miller's patients. Jane immediately focus on the name Jay Roth, due to Roth meaning Red. I think this is a red herring, and not Red John himself. Another patient is Mitchel Livingston Washburn, whom I think is the real Red John (Mashburn, Washburn, M/W upside down).
If this is true, nothing in Sophie Miller's recording about Jay Roth can be taken into consideration, which means that the part about a phobia is another red herring, which might lead to one of Red John's accomplices, but not Red John himself.
I guess several of the names on the list can be accomplices of Red John, but I don't want to believe that the majority of them are. Brett Partridge can for sure be an accomplice, but I don't think all of Bertram, McAllistor and Smith are.
I might have missed something here, but right now it's all I come to think of.
Anyways, my main suspect for Red John is Walter Mashburn, in the appearance of Robert Kirkland.
