In truth, I don't think any of them is RJ. 

It is a known fact that RJ has a really soft/high voice, and none of these suspects do. Of course, RJ might have been using a voice changer. But wasn't Jane kidnapped by RJ once and therefore should know his real voice? 
It is obvious that RJ has a organization, a powerful one, shown in the scenes where Reede Smith and Bertram all report to someone else. So I don't think RJ would go kill that PI girl himself. He could just have one of his many many followers do it. Therefore, the assumption that RJ has the tattoo is invalid. It could be that everyone in his "army" has the tattoo and he actually DOESN'T have it. 
How could RJ know the suspects before Jane? My guess is he made a bet. But it would be smart not to put he himself in the suspect list. He could just be the mastermind behind the scenes, pulling the strings, having his followers do the dirty work, so it's quite plausible that he is not even on the suspect list. 
As for Hafner and Stiles NOT having the tattoo, there's two possibilities1. They are innocent and have no connection whatsoever to RJ2. RJ's organization "teamed up" with visualize, so any visualize members are a part of RJ's group. Even though this is unlikely, I just don't get why in E06, there was the LONG scene regarding Visualize. And they've always been kinda shady in my opinion.