The same class will be easier than an array of classes.
AoE will be a strong choice too, since you want to blow lower stuff up quickly, rather than kill things which present a stronger challenge.

So ranged classes...
With AoE...

Possibly Mages or Warlocks...
Arcane Explosion or Blizzard.
Seed of Corruption is nice, as is Rain of Fire.

You might want a healing option.
Shaman can heal in their DPS (Elemental) spec.
They'll have Earthquake and Fire Nova, etc...
Fire Elementals, on a 5-min re-use timer (glyphed)... should be decent.

I've always liked Druids quite a bit.
For AoE they have Hurricane, Starfall, Treants...
Even outside of Moonkin form, lower level content shouldn't prove much of a threat.





While you have RAF, I'd level a lot of combinations...

Even if your current goal is older content...
You never know what you might want in the future.

RAF is only 90 days...
And it will get you a plethora of options, both for your current needs and have the option for other pursuits in the future.