The idea that finishers will be overpowered is grossly overstated. The fact is that in an average fight (data taken from many different style fights and difficulties. Source: worldoflogs.com) the damage dealt by finishers is around 10% of their overall damage with it being obviously higher for some specs and lower for others. Take one of the best and worse fights for a rogue on live right now, Sarufang 25H and LK 25H respectively. The highest ranking in the world a rogue of any spec has achieved in one of the best fights to be a melee is 75. In one of the worst, mostly because of a lot of target switching a rogue cant even reach into the top 1000. Giving a small buff to allow more use of abilities that only account for 5-15% of the classes overall damage and it being an obviously underpowered class wont make the class overpowered.