Currently, Subtlety can AoE through multi-dotting Nightblade
. Obviously, this has some major downsides compared to traditional AoEs (namely, it requires more effort targeting enemies, has significant rampup when there are significant target counts, and takes a long time to play out all of its damage). It does have some upside (namely, in a situation suited for it, say 3-5 targets that last 20-30sec, its performance is relatively high, or at least will be with tuning).
However, it also has another upside, in that when there are multiple targets around, but you mostly care about damage on a single target, you can funnel all of those tons of extra combo points into the primary target, skyrocketing *relevant* damage. With people organizing roles to maximize overall performance, you can do things like "You three fully-AoEing will be enough to kill the adds in time, so the Subtlety Rogue can maximize boss DPS." and end up ahead.
Over the course of a raid tier, this will occasionally be above average, but not usually. We'd certainly argue that the current situation is more interesting than just having an "AoE Eviscerate" finisher, and there's always going to be some variance in AoE performance between specs on any given fight. The question is: Is it too much performance difference in the typical situation, to be acceptable? We'd love to hear your thoughts on the matter.