Okay let´s  focus on the facts:

1.RJ is a Serial Killer -a rapist before he kills and therefore  it´s a man.
2. he kills Patricks Family because he wanted to teach PJ that he is not so clever ("if you were a true xy you don´t have to open the door to see what I did to your Family...) and he did this because he felt deeply insulted be PJ´s interview on TV.
Which means RJ is really creepy - he also felt insulted by the San Joaquim Killer and acted the same way- kill the one who he thought insulted him.
He did not kill PJ because he has a sense of admiring PJ´s Cleverness-as long PJ isn´t smarter as he is.(for this admiration he send Lorelai as a "Love-gift" first.)
3.he has a huge Network of Co workers for him - especially middle aged women- which means he can attract women easily by charme, Charisma, Money what else.
4. He likes sitting next to Rosalind when she´s playing the piano - I think this fits more to an older guy like Bret Stiles.
Rosalind is safe because she is blind and she loves him- the Person he Plays for her. the fact that she is blind makes sure she is honest and can´t be attracted by his fame as Visualize head. also he makes sure that she is his Possession (remember the little Smiley on her wall)
Even the description of Rosalind fits- straight hair and the physical attributes.
5. the Smiley on the Red Barn doesn´t have to be painted by  kid only someone pressumed this. Fact is:  it was painted in the 80-ties by someone Close to "Visualize"- it´´s RJ Symbol like Visualize has a Symbol. so it´s RJ personal note.  RJ could be without any Problems now in his fifties..
6.  Bret Stilesknows that Lorelai is becoming  a future Problem when he helps PJ to free her from prison and he could be prepared  when she leaves his Network and hunts for him.
7. The man who was killed in the Hospital was a Close "friend" to RJ - so does anyone think Patridge could be so charismatic to womanize all that Ladies and rule to all the established middle aged man? It must be Stiles to my opinion. Kirkland is working for RJ. Aweful smile on kirklands face when PJ finds Lorelai....
8. "Visualize" Keep their Windows Close for Police Investigation so RJ is able to Keep undetected for a long time. He also thinks he can threaten future murders because he feels secure to rest covered among "Visualize".
9. RJ is a great Showman (like Stiles), he is really clever and manipulative (as Lorelai said).
His first choice is Power (he predicts the rules- in 5x22 PJ "changed the rules" and the threat has to be future punishment for Patrick- so RJ is in his daily Life in a powerful Position.
He is sadistic  and attracts sadistic networkers by letting them having their pleasures (the Sheriff son who hold the trapped rich Girl in the Basement of a barn and was shot by Patrick...) this means RJ has enough Power to make sadistic People submit to him (f.e by means of Money or whatever).And he likes to watch/study the dark sides of his workers...
10. he seems to be attracted to red haired woman (Rosalind, Kristina,Brenda, Rebecca and yes: van pelt!-look how charming bret Stiles is with Van Pelt...
11. in 5x22 when Lorelai reads the letter makes compliments with PJs work  and says "bravo"- it sounds like Stiles style...
For me all points to Stiles- only disturbing thing is: PJ teaching Betram lessons in poker Face... There Betram was unable to loose a poker game which reveals also a very vain and power possesed character... this is my suspect number second- also I think Bertram doesnt have enough Charme and Power to make all these people work for him.