I have done this - 2 boosters, with 4 alts each, and each booster running in their own dungeon. Not easy but doable. Mage is for sure a very good choice here. They can blindly aoe without targeting and melting the mobs all the way before Northend.

The key is to align the 2nd booster to the first booster while navigating in 'same' dungeons.

My plan is actually 8 monk, without RAF. Will do it if RL hobby doesn't eat into the wow time.