I was a level 33 mage, and I saw the group before I had any idea what it was. I had a sorta what-the-hell moment, and ran into the middle of the group, frost nova-ed them, and then used blizzard while they were all frozen. Once they dethawed, they chased me so I just ran around in a circle using arcane explosion until only the courier was left, then I magic missile-d her to death.