As it was before; the stat priority will change depending on your role. Take this with a grain of salt (because I could be very very wrong) but if I remember correctly a disc priest in 10m (no role specified) should aim for a balance between all stats with a preference to the following order; Mastery > Haste > Crit, mainly due to Haste being a potential buff brought by other raid members and Crit rising with your Int.
So; Mastery = Haste = Crit is the aim but due to raid buffs; Mastery > Haste > Crit.
As for PvP goes it depends on if you're going for arena or if you want something to play around with in PvP. Spell pen to cap (for psychic scream to not miss/resis), spirit to where you're comfortable and after that it's usually between resil or mastery.