My team of druids, having done Ramparts once and Blood Furnace once, and playing entirely with rested was 64th before leaving Hellfire. I remember needing to run Ramps/Furnace, to be 62nd before hitting Zangarmarsh; I'm not sure what they did to BC leveling, but its a lot faster now.

You'll be better off with a team of 5x, then you would be with say a 3x team A and a 2x team B.

With one team, they all advance together on kill quests.
And you have to painfully do the collection quests x5, if they're worthwhile for opening something or giving a reward.

With two teams, you need to run the kill quests twice as many times.
And still end up doing the collections x5, just x3 and x2 in separate doses.