You could add an Elemental Shaman to either or both groups.
The Shaman brings buffs that are generally an overall DPS boost to a caster team.
Even if the Shaman is not Healer spec, they can queue as a Healer for the dungeon finder.

A tanking class is one of: Druid, Paladin, DK, Warrior.
Of these, the Druid can be an effective ranged DPS class.
While the Druid or Paladin can be an effective healer.

I'd probably add an Elemental Shaman and Paladin to one team.
(Whichever you'd like to take furthest in PvE type stuff).

And then an Elemental Shaman and a Boomkin to the other team.

You could ditch Shaman on both teams, but I really like Shammies on caster teams.