Assassination seems to be the way to go. It's not as flashy as some of the other melee but Rogue's have never been about that. The gameplay is fun and that's what matters in the end. The artifact weapons look sweet (every skin available) and I have been enjoying myself as Assassin on the beta.
Would be great if we could get Ambush back though. Seems silly to be called "Assassination" and not actually have a skill to open up with besides mutilate from stealth (garrote isn't worth it imo).
Also, Kingsbane FeelsGoodMan