For any story to be truly entertaining, there has to be some plausibility in the story itself.  That doesn't mean that we have to believe that the story DID happen, just that it COULD happen.

Mr. Heller and company are in serious risk of pushing the boundary of believability of this story beyond the bounds of plausible entertainment and into something we all just shake our collective heads at, say a collective "pshhhhhaw", and walk away from.

Some of the things I find incredibly difficult to believe:

1.  Tom McAllister could make that voice,
2.  Tom McAllister could seduce a woman like Lorelei and get her to do anything he wanted,
3.  Tom McAllister could seduce the blind woman Rosalind Harker,
4.  Tom McAllister could seduce ANY woman,
5.  Tom McAllister could convince any male followers (such as Craig Laughlin) to do as he wished,
6.  Tom McAllister would have the means (time, money, resources (such as transportation to Malibu and Mexico on a moments notice from Northern California at a moments notice)) to commit the atrocities that were committed by Red John all while remaining Sherriff in Napa County,
7.  The FBI has the authority to simply disband a state agency such as the CBI (there is still something known as state sovereignty covering such matters),
8.  A person with great insight into human behavior (such as the character of Patrick Jane) wouldn't have put two and two together when coming across a beautiful American woman in his hideaway in Mexico just a day before the FBI shows up to make him a "deal".

These are just a few examples of things that seriously stretch the bounds of credibility within the show.  If the story continues on this arc, then soon it will become SO unbelievable as to be completely unwatchable.