However, the episodes with Red John highlight the problem of Red John, and I don't mean "problem" here in a plot sense but rather in a boy-that-is-dreadful-writing sense.
A suitable comparison is X-Files since Red John carries the same weight and purpose as the aliens on X-Files. Just as the aliens--at least for Seasons 1-6--are never definitely present, Red John is never definitely present. More than anything, the aliens represent Mulder's fate or destiny. Or, rather, they represent the vastness and mystery of life with which Mulder tackles. In many ways, Red John represents the same thing for Jane.
Despite the analogy-taken-too-far factor, the idea of Red John as a force does work. Since I adore Simon Baker, and I like procedural shows, and most of The Mentalist's episodes are procedural, I tend to treat Red John references this way: he represents the chaotic, unknowable side of life.
Until an episode focuses on him, and then everything about the character makes nonsense of everything else.
The idea of a master-mind criminal who has his fingers in every pie and can flip any agent and access any storage locker and bribe any poor slob to take his place, etc. etc. etc. undermines the whole CONCEPT of a procedural show. It means that in every episode, the bad guy could be a pawn of Red John. Every case could have been sabotaged. Every agent could have been gotten at. Nothing is dependable. That isn't a profound statement, by the way. The ultimate conclusion of Nothing is real is So why do advertisers want to pay to keep this show on the air? and the ultimate conclusion of that is No more show, which is very sad and kind of undermines the whole purpose of entertainment.
The absence of real meaning does not make things better. It just makes them boring.
(I believe John Lenin was a great musician, but "Imagine" has got to be one of the dumbest songs on the planet: "Let's erase everything that makes life interesting and valuable. At least, we will have peace!" Yeah, the kind of peace that numbs the brain into oblivion.)
And yet, Chris Carter more or less made the omniscient enemy work.
I've thought about why, and I think it has to do more with the writing than the concept. In fact, I think it is entirely possible that The Mentalist writers are in fact aiming for Carter's alien-effect. In Season 2, there's a fairly well-written episode dealing with the shooting of the cops in the CGI building. There are some fairly silly implications (Red John, again, is working through someone, and the ending relies on yet another deus ex machina), but the episode is actually quite tight.
And I think the reason is the same reason Carter's alien episodes usually worked: the episode stays focused on single characters with single motivations, however complex, who are held to the laws of probability.
I have a theory that The Mentalist writers know this. I think this is one reason Red John is never paid off effectively (and no longer can be in any real sense). The writers introduce fantastically interesting characters: Hightower, LaRoche. But these characters are more interesting as themselves than as Red John's minions. LaRoche with his cool, pointed questions, his fluffy dog and Hummel figurines is a GREAT boss. (In fact, the whole Red John plot is almost endurable just for giving us LaRoche as a by-product.)
So when it comes time to do the big-reveal, the writers shuffle it off on a nobody, like Grace's fiancé as Red John's mole (he has one? the guy can get moles so easily, I was sure he had about twenty). That was surprising but made no sense and thus, was kind of stupid. (And the fiancé was more interesting as Rigsby's rival.) If it could be him, it could be the guy at the water-cooler. Hey, it could be that guy in that one episode that one time who . . . I mean, who cares? I'm glad it wasn't LaRoche since that would have ruined a perfectly good character, but who cares in general? Let's move on.
For most of X-Files, on the other hand, Carter managed to keep the focus on the probable despite the show's improbable premise. Now, that's a feat to be applauded!
Still, I will keeping watching my Mentalist, only keeping in (my) mind that Red John is an amorphous force rather than a flesh & blood enemy. That way, the real flesh & blood crimes investigated by Lisbon's team will actually matter, which is what my give-me-a-good-mystery-and-the-world-is-my-oyster soul wants in any case.