It will root anyone that attacks the priest with melee abilites (all melee at once), yeah its a pure pvp talent like (deep freeze, metamporhosis etc.) and as for PVE, I mean spriests really shouldn't have an issue (imp spirit tap, shadow fiend, replishment etc). But if it can root npcs that would help priest to some extent in pve with the health and it actually being able to CC something. Or actually you can add in, if the aura fades from the priest and he did not take any dmg during the time the aura was active, the priest gains 250 spell power for 20 secs. Just like they did to dispersion on ptr (but end up removing it).