PVP, you'd probably do best with a tank/dps and healer - DK, Pally, etc, with a priest or druid?

Dual boxing for leveling is the easiest way to go, hands down - you may find that with RAF, you can get a whole bunch of characters up to 60, and be able to pick and choose which classes work best. I've started a long list of characters, which I left at lower levels, that I will be going back to and leveling with my RAF.

That's the key to RAF dualboxing - don't limit yourself to one team, make the most of it. Get the free levels now, and then breeze through content later.