I must say I really like the mastery system.
It's basically replacing passive talents, and good riddance. For example; the holy paladin tree will grant you stronger heals, spell crit, and extra critical healing bonus (Increasing crits beyond +50%. woooo!) simply by taking talent points in the holy paladin tree.
That way, you can pick fun talents instead. Like body and soul.
A very open question is - what masteries do you want to see on the priest?
This is my speculative guesswork based on existing passive talents. And remember, numbers are adjustable.
- Damage mitigation: +1% stronger shields (PW:S, DA) per talent point spent
- Spirit: -0.5% more spirit per talent point spent (the new spirit stat, that is)
- Haste: +0.15% faster cast time on all spells
Holy: (pretty much identical to the holypaladin, booring I know)
- Healing: +1% stronger healer per talent point spent
- Critical Healing: +0.15% more crit on healing per talent point spent
- Critical Healing Modifier: +1% more critical modifier bonus per talent point spent
- Shadow Damage: +1% more damage by your shadow spells per talent point spent
- Hit: +0.15% more spellhit per talent point spent
- Mana efficiency: Shadow spells cost -0.1% less mana per talent point spent
That said - which masteries do you want to see?
Also: bye bye to 38 passive talent picks in the holy tree. Cheers!