Vanilla Rogue here - and I've been playing the hell out of all the rogue specs on the Alpha. I've come to the conclusion the Outlaw spec is pretty exciting and fun to play. Assassination is still very similar to live with some good changes and some, imo, bad changes. (I have mixed feelings on Sub but I'll leave it out of this thread for now).
When I was playing Outlaw, I couldn't help but feel Killing Spree no longer really fits the Outlaw theme anymore, and they already have a CD in Adrenaline Rush. I also couldn't help but notice Assassination lacks an AOE finisher now that Crimson Tempest is gone. You build up CPs with FoK only do tab-Rupture/Envenom for the poison buff and just keep spamming FoK.
It's a pretty anti-climatic build up of CPs because there is no good payoff.
I think a good solution would be to move Killing Spree to Assassination, where it fits more thematically, and make it their AOE finisher (adjusting numbers accordingly).
The gameplay mechanic for this would be like:
FoK spam until 5CPs, then Killing Spree, which will do it's normal sound/animation/mechanic and strike all targets currently afflicted by your Lethal Poison (since you've been applying them with FoK).
Killing Spree is a really cool ability. It's fun to press. And I think it would be cool to have it as a payoff button in your AOE rotation as Assassination. I don't think it would be a major loss for when I play Outlaw because there's already quite a bit of interesting mechanics and fun there, and I actually think Killing Spree feels mechanically weird for a more sturdy Pirate theme where you're pulling out a pistol and whatnot.
Assassination lost it's Dispatch mechanic which actually was where most of the spec's fun was. RNG procs plus looking forward to an execute phase. Now there's really nothing enjoyable about the spec. It needs something fun. Meanwhile Outlaw has a Dispatch-like mechanic in the Pistol Shot proc through SS, then Roll the Bones, Bribe and all kinds of crazy shit (love it) - I think they can lose KS and still be really fun, especially since Blade Flurry is a solid AOE.