I personally doubt that Red John is among the 7 Suspects. The plausible suspects - If we go by Rosalind's description are far too convinient and IMO unworthy candidates to be RJ. 

Brett Partridge for example. 
Sure he seems like a nutcase but he absolutely has no charm no is he similar to Patrick in anyway. Most RJ accomplices that have met Patrick made a point to liken the two. Unless Brett can completely shut down his calm and manipulative personality then I dont see him as a candidate. 

The descriptions aside, he doesnt at all seem like the kind of person people would follow. 

Bob Kirkland
He is somewhat of a charmer and is very hard to read. I remember Lisbon saying he talks as if he is saying nothing. His interest in Jane and his position in the system would grant him quite a few perks and tools. Though he seems like a Red Herring IMO and he is not much like PJ. 

Id much rather appreciate him being tied to a different storyline or his own pursuit for RJ for his own personal reasons. Some people think he had a connection to Miranda, IMO that would be suitable. 

Ray Haffner 
He is a charmer il give you that, but he does not possess the qualities RJ is rumored to have (By his accomplices). RJ loves playing games and he likes winning, evident from the season finale, Ray couldn't even last a day with Patrick and he was annoyed with him quite a few times. He also seems sloppy. 

What makes him a candidate is his physical description, which ties in with what Rosalind described and his past on the farm. He would be a disappointing RJ IMO. 

Those are the only suspects from that list that I see as plausible.

Krystina IMO would be much more satisfying as RJ than anyone else though. The reasons i want to give have already been covered here and then some.