I've actually been running with 5 since launch. I've got a Warrior as tank, Pala support, Warlock/Mage DPS and a priest healer. I've just hit 30 with them all. I've been driving from the tank, as I find it easier controlling mobs etc.

I've avoided as many quests where I need to collect x amount of items. I've just tried to find all the kill x amount of mobs quests, even that's a ball ache sometimes with everyone camping spawn points. Though I'm able to successfully run through dungeons without any issues for the right levels. I take a bit longer than other groups, but all the loot and drops are mine. I've got all professions going as well, which seem to be at the right levels. I have over 6 days played on them all, so I think it's taking a lot longer than normal but loving it so far!