State of shadow priest

Hi, i want to start playing cata here on warmane, and i want to know how is the state of shadow priest in pvp and pve
I want to know which tier is shadow in 2s(low, medium,high) and 3s :)
And extra question i heard that gurthalak voice of deeps is really op, is that true or?

idk about pvp but in pve its pretty good but still need some fixes to DP dmg (ticking for lower than sw:p) and gurthalak not rly..just for paladins