I jumped into RFC today at 12 which I thought was do-able at that level with 1warr1priest3mage, but coming up to the 3man trogg groups I simply ran out of mana on mages, it took close to 50% of mana to kill a single mob.
I might need to revise the idea of doing dungeons from level 12, I did all the easy quests in barrens ( no loot quests ), maybe I need to be 14 or so before hitting RFC.