First - Blade Flurry makes all used abilities effect another enemy nearby but energy regeneration is reduced by 30%. This includes kidney shot, Garrote, Cheap Shot, Shiv, and dismantle.(Possibly Gouge?) This would mean people in RBG's actually have a use for rogues, even though we have utility, CC, ninja caps and whatnot.
Second - Bring back Improved Sprint and make it baseline. This will help with rogue mobility everyone is complaining about.
Third - (This might be a little OP) Killing Spree remains how it is now BUT if there are multiple enemies, Killing Spree does 200% damage. This would help in PVP against classes with pets where this ability becomes useless. In PVE, it would only be beneficial in mobs and AOE where AOE damage doesn't really mean anything...
Last - BRING BACK FAST OFF-HAND SWORDS AND AXES
I know that these are more or less based around combat, that's because I play it the most.
I have a 90 warrior and shaman, coming from the views of those classes I don't really see these ideas being OP.
Feel free to comment and give criticism or even add on to what I've got. I could really see these being part of the game and bringing back the rogue community.