Spirit makes a noticable difference in mana regen.
However it is not worth dropping other primary stats for. in pvp on a lvl10 your best mana regen strategy is to get out of combat for a couple seconds which restores all your mana quickly.
yes it is but you lose utility, the snare is really only good if someone is trying to run away, i.e. wsg, not really for duel. and imo a 10 spec HAS to be viable for 1v1.
the snare would be great in a 3v3 team. for 1v1 disc is superior, however a shadow priest can easily burn most classes down. Aaw destroyed Ioerror on his shadow Priest
I haven't really had much chance to straight up duel 10 priests, but i know that whn i meet Podie in AB, if its a legitimate 1v1 it is usually very close. But thats Podie.
By close i mean i usually barely win, or he runs off.
I personally just stack mana as best as I can. Spirit doesn't yield... much in combat regen at all. I mean I'd take 1 int for +15 mana over 1 more mana regen/5 seconds in combat.