I've never leveled many groups beyond level 20 except for my warlocks, but that's because I love the class make-up so much.



All the DoTs mean not having to stop while running around and killing things. Felguards in large quantities are ridiculous. I always have soulstones and healthstones. I can easily summon people if needed.



More recently, I'm learning that demon form for multiboxed warlock groups is incredibly powerful. Even at level 70: 400-ish damage per second for 15 seconds X 4 warlocks? That's absolutely evil.



I'm looking forward to leveling mages though. I think that having 4 X mirror image will be even more entertaining.