I think all the "clues" and "hints" are simply diversions and deceptions
from the writer to keep the audience thinking and off track about Red
John's identity. There are so many, and quite frankly many plausible and
realistic theories about Red John's identity.
Bruno Heller is a great writer who plays with our minds, week in week out with his writing and his interviews about season 6.

Heller and the writing staff gave every suspect his moments for and against being Red John.
But
someone already said it. The chase has been on for so long... the
reveal of Red John has to be mindblowing, or else many viewers will be
hugely disappointed. I therefore think, that will not be as simple as it
being is one of the individuals on the list.
It has to be someone else entirely (Kirkland's Twin, Ardiles, Mashburn, someone Jane knows from his past) or at least two of the suspects on the list.

And
I still strongly believe that Grace is Red Johns main accomplice. I always
have the feeling, that when Van Pelt gets any information about Jane
being close to catching Red John someone important to the case dies,
just like the tracking.

The last thing, is regarding RJ's tattoo.
Is it really three dots on his shoulder or another deception? I mean,
the PI says he has a tattoo on his left arm and touches her left arm.
The three dots are the result of her fingertips being bloody. So are the
three dots just a coincidence? I mean where would she have seen a
tattoo on the shoulder (not to be seen unless, the person wears a
sleeveless), would RJ be so careless to reveal sth so important, or was
it a tattoo on his forearm (which is much more visible and revealable).