I haven't even played this expansion but I can answer your question for you:
3) Doesn't fucking matter, reforge that shit to crit
Haste is shit for PvP because you need tons of it to get even the smallest decrease in cast time. Mastery is shit because, well, what would you rather have: a 2% chance at a wild quiver that hits for the same as your auto attacks or a 1% chance to make all your attacks (including aimed/chimera) crit? If you have to choose between mastery and haste, take mastery, but don't obsess over it. A couple percent of haste vs. a couple percent of mastery will not matter enough to swing any matches your way.