I picked one of the new realms to start over on and created 4 out of my 5 characters (the fifth is a Blood Elf Paladin which I can't get until Tuesday) and leveled them up to 6 together.
Blood Elf Paladin (not created yet)
The technique I'm using at the moment is to have everyone follow the druid (this will change to the paladin once I get him up and running). When they are within range the warrior charges while the druid drags the other characters around behind the creep. Once behind the creep the rogue backstabs and the shaman earth shocks. At this point everything is dead by the time the backstab, charge, earth shock and autoattacks go off. Long term the druid will likely be in cat form doing shred with the paladin just healing everyone and dragging people into proper positioning with auto-follow.
My quest to level 5 World of Warcraft characters at the same time.