Lets think about a couple of things. Why hasn't RJ killed PJ when he had the chance (he can still easily kill him). PJ is clearly quite a big threat to RJ, so why not get rid of him? He usually kills anyone who is a threat to him (e.g. Bosco). Why does he try and befriend Patrick? Personally, the only thing I can think off is that RJ needs Patrick's help for one reason or another- maybe the RJ wants to bring down the "Tyger, Tyger" group? I am probably wrong though.

Now, the main question, who is RJ? Haffner fits all the descriptions given by Rosalind Harker and Sophie Miller. He is also a member of Visualize, who IMO will play a key role soon. Add that to RJ letting Lisbon live when he had an easy chance to kill her and the fact that Haffner clearly really likes Lisbon.