All Red John's accomplices, Red John is a made up name which started with one murder the same as "Blair Which" project and all myths which were recreated by multiple people/beliefs. Take the "Scream" scenario where multiple people wore the mask yet the original killer was never revealed. Myth.

People often tend to follow an "Idle" in life.. Whether it's a famous soccer player or actor. For the people who have had bad experiences in life e.g. have been bullied all their life.. Why not a serial killer as an "Idle"?

Another theory, the actual Red John has long stopped his killing spree and others are now doing it for him thus he can never be found. You cannot find someone who is not hiding from things he has not done... 

There was one episode where Patrick was put in a Limo when Red John spoke to him via a cellphone (He thought he was in the Limo) which leads to conclude that Red John has his apprentices as well, people who do work for him yet have never met him... "I just do the job and ask no questions"