Best dual class combo for aoe damage

I've been playing with my sister lately, me as a shaman and she went pally, leveling up on lordaeron. When leveling, we had a lot of success by doing a pull all then wipe strategy, where she ( tank ) pulls all quest mobs we need and then we use skills like consecration, fire nova and chain lightning to kill all of them fast.
On another pair of characters, tank Druid and holy priest, we couldn't do te same. Swipe deals very little damage and holy nova uses too much mana.
I was wondering what would be the best class combination for aoe damage? It would need some sort of tank so someone can hold the mobs while the damage goes in. I was thinking maybe warrior and mage? And as for mages, what is the best aoe dmg spec?

pally tank and balance druid

I'd go with the Pally tank and Balance Druid as Swarmer said above.

-Pala tank can always use hand of protection and such to protect the druid incase any mobs attack him
-Extremly easy to hold bunch of mobs with paladin with Seal of Command.
-Paladin can heal himself so he doesnt need that much of an external assistance so druid can focus on doing the AOE and not healing him
-Balance druid as we know is just insane when it comes to any sort of AOE + incase of emergency he can switch to bear form to survive or heal himself or the pala tank.

All in all, Druid + pala tank is amazing.

Altho bare in mind 2 classes that require mana for leveling could be a bit boring since you would have to make constant mana stops haha.

What you could also do is help your friend with druid to hit 55 then you can make yourself a blood DK, it would be a great combo. DK is just insane for leveling.