I've got a 5x Discipline Priest team sitting at 60th, from RAF.
And a 5x Hunter team also at 60th.

I could see either group being a force in BG's.

Hunter's have strong single target DPS.
And Volley is not weak either.
Plus 5x traps, Concussive Shot on round-robin, Pets flapping around in people's faces...

The Priests were a surprisingly easy team to level.
A solo priest is a pain, unless shadow, but I did not notice this for the team.
I envisioned them as sitting back and playing massive support.
But a Disc priest has potential for a fair bit of damage too.
5x Mana Drain would be fun vs casters too.
Pain Suppression, PW: Shield, Power Infusion, 5x Mass Dispel (love ISBoxer mouse broadcasting), was thinking of Fear Ward on round-robin, on the lead toon and an easy cast Mass Dispel vs fear.
Prayer of Mending on each of them for supplemental heals.
Penance can be OP at times.

Too many good combinations to try.