Who is the best rogue in wow

There is no exact answer to your question, but one of the top rogues in the world would most likely be Neilyo (sponsored by SK Gaming, 3k rating, aka rating cap, in 2s/3s/5s). There are many other known rogues out there who are equally as good as Neilyo 1v1, but in the longrun Neilyo would be better than them due to arena ratings... There may also be an unknown rogue out there who might even be better than Neilyo but hasn't shown his face yet. But in either case, Neilyo is most likely one of the best/most skilled rogues in this game.

Btw another good rogue who's working his way to 3k in all brackets would be a rogue named Reckful on BG9 (Blackrock), 80 undead rogue.