Lets for a moment think of the Red John case as we would any Mentalist case. In each case, there is a certain amount of information and misinformation. Jane controls what the characters see and don't see...often misleading them in order for another truth to ultimiately reveal itself. Same goes for each case at the level of the show. As viewers we are led to believe one thing, be it through a suspicous behavior, thematic continuity, or outright misdirection. The hope is that the ultimate outcome will be satisfying and surprising.
There is a lot of information or "clues" our there as to Who Is Red John. It can't all be true because the sum total of all the subtext, symbolism, and concrete clues do not all point to the same thing. Much of it (or most of it) is misdirection and this manipulation is happening at many levels - plot, thematically, and what is being said about the show by those who make it.
With all this in mind and assuming you have been reading all of the fantastic theories on this board of which this is a synthesis, I think there are three options for who is red john, depending on what information I choose to believe:
1. Ray Haffner - the above the board, overt clues and deductive reasoning point to him. If you trust the show (and and the list), then he is your guy. The misdirection is happening at a symbolic and thematic level (pigeons, for instance) and its purpose is distract us.
2. Brett Partridge - the symbolic and "under the radar" clues apear to point to him (such as the 7-headed dragon theory, which is great). Dead or alive. Of the seven suspects, he best fits Heller's statements about him being a person who has been around from the start. The misdirection is happening at the plot level. His death serves to thwart expectations and cause us to mistrust our judgement.
Option 1 and 2 actively work against eachother, distracting us from our third option:
3. A non-List person. In this case, the show itself would be propagating misinformation. We tend to think we can trust Hellor, as show creator and mouth piece, as well as CBS advertising and press releases. But why do we assume this is a sacred contract? This is the only reason we have to believe the the list is for real. It is not neccessarily supported by the plot. There is precedence for Jane lying to the team in order to solve their case. And Hellor, as a proxy Jane, would be lying to us for the good of his show. One could argue that this list being fake is foreshadowed by the presence of a fake list in episode 4. Jane's fake list is full of men guilty of other crimes, and so is Heller's fake list. One is full of pediphiles and drug dealers; the other of corrupt cops and cultists - probably people who RJ wants dead anyway. Like a good mentalist case, we are being lied to in order to create a wrong impression so that the ultimate reveal will be both surprising and satisfying.
My optimistic lean is for option 3.