Blizzard woke up, after 3 months of broken PvP
We have made burst nerfs to Retribution paladins, death knights, Arms warriors, Arcane mages, hunters, Feral druids and now rogues. Almost unanimously, the nerfed classes thought that nerfs were needed but that our specific nerfs went too far. Nerfing classes is never fun. Players hate it, and ultimately it means we screwed up or at the very least failed to predict new tactics. But we still need to do it for the good of the game when we think it is warranted. There will be more. (Source)
As for Rogues, well, cry now.
Rogue (Skills List / Talent + Glyph Calc.)
More changes to come in 3.1
On the second question, yes, we have several changes in mind for 3.1 for rogues and only announced a few. (Source)
We agree with you about how an Assassination rogue should play – setting up a kill and then delivering it. But bursting someone down who is crowd-controlled while the victim has very limited decisions they can actually make to avoid death is only fun for the rogue. The Mutilate button push is just very strong when poisons are nearly always on the victim.
I have said before that we don't think Arena is fun when healers are immortal until mana-drained. However, we also don't think Arena is fun when someone always dies in the opening few seconds. The matches need to last long enough for something to actually happen -- for you to decide who you are going to attack or how to respond to their actions. If someone literally has almost no response for your attacks then that is not skill that is allowing you to win matches (and I am not just talking to rogues here). (Source)
"I have said before that we don't think Arena is fun when healers are immortal until mana-drained. However, we also don't think Arena is fun when someone always dies in the opening few seconds."
This pretty much sums it up. Dev's stated that in order to give arenas some balance, they were boosting dps a little bit. What i think is that, they never had a single experience of game play prior to that comment being made. Arenas aren't 1vs1, and if u run arena 1dps&1healer, thats ur call. With this change in this expansion, what we saw was an increase in DPS representation in arena. Why? Shutting down a healer was never so easy, so why not make it even more quick?
All in all, im glad the change finaly came.