1: Crit is in no build better than both mastery and haste, in GoSac builds Mastery pulls ahead due to more damage being focused on yourself (pet doesn't benefit off mastery), in GoSup Haste pulls ahead due to your pet's energy regen benefitting from this. Crit is always middle stat if I recall correctly, but you know what they say: Not 100% sure? Sim it! If you reforge to what a sim says, you then sim again, and it still says the same, you're basically good
. Otherwise keep reforging slightly to what the sim says etc etc. (I don't think reforge plots work very well, I can't work with em that well at least, awesome for you if you can).
2: Sup has been said to usually be ahead, but Sac is supposed to not be a bad choice either (apparantly they're really close, but I have yet to see someone grinding out a full gearset optimized for both to tell us more precise numbers, most posts are rather vague.). Don't know why GoServ falls so far behind, I guess there's very little fights at the moment that require on-demand burst where it's okay to sacrifice DPS during the rest of the fight (read: no spine as of yet)
3: Keeping in mind the 30% nerf to the speed of the adds, which equals to 1.5 waves more or less (20% speed per wave): I can get 5 waves post-nerf with Affliction, but seemingly infinite with Destruction (6 was easy enough pre-nerf). For the rest of the fight, Affliction is better. So I would say, if you're 25man, and you can be assigned so that there are others able to compensate for your shit DPS in P2, go Affliction definitely. If you're in a 10man, and you really need to get more waves in P2 than you can pull off, go Destruction, getting 1 or 2 extra waves on both transitions equals 20-40% more DPS on the boss for the entire raid during the second and third P1. Considering more than just me had the problem of only being able to handle 5 post-nerf, I just stuck with Affliction. (Perhaps I could've done better if I had looked up some Affliction specialists guides on soloing a single Charge, but Destruction is obviously easier, single Chaos Bolt and Conflag usually did most of the job)