A thing often overlooked when building a team is armor type. Covering cloth, plate, leather & mail is a huge advantage. If your team has the ability to spec melee rather than casting only, that's another + if you want a change. If you run enough dungeons you'll gather enough off spec loot anyways.

The holy priest is a very strong choice with the lightwell, since it can be macro'd.

Pally tank,
Boomkin
Ele Shaman
Lock
Priest
... would be my choice.
Mage is a strong choice for portals & CC as well. I'd replace priest for mage then:
bear tank,
pally healer,
ele, mage & lock dps.