If i was to make a new caster team with everything I know now:

Pally tank (healing offspec for pvp).
Shadow / Disc Priest
Boomkin / resto druid
Ele / Resto Shaman
Mage or lock. Mage is handy for food + teleport. Lock is more fun + gives 13% buff.

This would cover plate, cloth, mail & leather and give me the opportunity to go with the healer that fits best the encounter.

If i was to build a melee team: pally tank + 3x dk + disc priest