I would like to put a nice little comment here.
JUST to make it clear, exhilaration is by far the most useful of the talents in that tier for PvP. Aspect of the iron hawk won't help you as a survival cooldown if you need a self heal. It's incredibly valuable for each spec, though I didn't even know there was a debate about it. Survival has absolutely no on-use or passive heal, making exhilaration a need for the spec if you're PvPing with it. Marksmanship has no large self heal, making it valuable as well. For BM, if you use stampede defensively (for spirit mend), and then exhilaration later, that's more defensive cooldowns than either survival or MM. Not to even mention, with readiness exhilaration's just that much better.
As for powershot, it is in my opinion (and quite a few others'), the most useful and overpowered ability in the game. I rarely use it outside of when rapid fire's buff is up, due to the 2 piece bonus of gaining 3.2k more pvp power when rapid fire's up, except for a knockback. Chain CC and enemy escape trinkets should be taken into consideration before powershot-ing, but the results are often comical. Glaive toss is nice, but it eats up globals and doesn't do much damage through the overall course of an arena. Barrage is in my opinion the worst of that tier due to it being able to randomly hit people other than your target even if they're very far away, or even LoS'd occasionally. This makes barrage next to worthless, because it's capable of breaking CC unintentionally.
Another point is, hunters do not have passive damage-mitigation (such as feint/elusiveness, shield wall, ect.) outside of aspect of the iron hawk which is ridiculous to even consider taking. Because of this, I think it's important to make it a point that PvP resilience is more vital to us than almost anything. If you want to be competitive in 3s or even 2s, have at least 65% PvP resilience is a must. To do this, you need to stack it. You lose out on some PvP power, but there's little of a difference to be made. I still hit for 30k arcane shots, I still hit 200k powershots, and I still hit 90k chimera shots AND take reduced damage. This is a must for competitive PvP.
Along with Marksmanship, for PvP and PvE alike you have a hard cap of 25% crit. In my opinion there isn't even a point to play the spec if you don't have that much crit, due to the way careful aim works. I also want to make it a point that hard casting aimed shot is next to useless. It scales with weapon damage immensely, however it does not scale well with PvP power at all. Not only that, but it drains you of focus more than anything else. I can't even think of a situation where hard casting aimed shot would be more useful than hard casting powershot. It is a must though, to use your free aimed shot once you have the required stacks for it.
This guide is somewhat helpful if you're new to hunters. It's something to work with give or take, but I highly suggest to not follow it intensely. I suggest for new hunters to watch and pay close attention to streams of highly rated hunters and dig around new and old forums for useful techniques, but do remember to not take everything to heart.
Just a quick question (might be a silly one), does mastery for bm hunters improve the damage of pets summoned through stampede?
Yes, which is why BM has nearly the best and most mobile burst in the game.