I've been debating the best way to go about this myself. I started classic three boxing. Priest + 2x Mage. I did three because I didn't think my computer would handle 5. Well, it appears it does, so now I'm trying to boost two more mages. I now have a 3 lock / 2 mage team, but I'm wondering if it would be faster to just pull the 2 lock / 2 mage team with a 60 rather than level three...