All of the above.
Do RAF, and get a lot of combinations.

I found 5x Priests, can one-shot via Smite.
And leveled faster than Elemental Shaman, Boomkin or Hunter teams.
Elemental did not drop mobs with 5x Lightning Bolts (although being able to cast while moving would definitely boost their speed now).
Boomkin could one-shot with 5x Starfire, but not 5x Wrath.

Ferals are extremely fun, and have for me leveled faster than any other composition.
Elemental Shammies are very fun.
I have enjoyed Warlocks (with a Priest), 5x Holy Pallies playing as Shock'adins...

Lots of things are fun