I think Bret is Red John. He has his official followers in Visualize, people can be really devoted to him. We know that in Visualize he helped some addicts, he showed them how to fight their weeknesses...just like Red John helped Michael Kirkland. Maybe Bret lets his most devoted followers to know also his "dark side", help him with the murdering, cover up if needed. I think Ray Haffner is one of those followers.
We know that Red John has been to jail - I don't think an ex convict can later become the chief of CBI or the Police. That's why I exclude Bertram and McAllister.