Gilthresa's post is pretty accurate.
As best healer I would says Priest. Disple and shield are way too powerful. For solo play as healer Priests are most effective. In group play this can change.
I've played a priest, all specs since 2006 and I love it. Good amount of CC's if you decide to spec Silence. Blackout is a pretty decent CC's as well if you have a flag carrier run away from you and you can't keep up, just spam rank1 SW and eventually he will be stunned for 3 seconds wich gives you time to catch up and fear.
But yeah, this mostly goes for Shadowpriests though but healing as a priest is pretty fun, compared to shamans I think, wich probably is the most boring healing class to play pvp.
The disc priests we had in my PvP guild all specced 5 points into shadow for blackout, typically with a build like this.
Well "Blessed Recovery" isn't too bad, quite good against physical dd's and it looks quite cool. I mean it'll procc the entire time against those classes. + a point into "Holy Nova" wouldn't be too shabby either.
I'd rather PI the mage, tbh.
Dunno if it does or not, but you can follow one up with another.
Well, if only priest could handle physical damage and the bubble had more than 10% scaling.