I've 6-boxxed EQ way since probably 2000, but stopped once I started WoW. So I have extensive experience boxxing EQ (at least 6-man).

My group was SHD, SHM, CLR, ENC, ROG, DRU. Knowing what I know now about multi-boxxing, the fewer the classes the better off you'll be. EQ, unlike WoW, is very heavily dependent on buffs, so I agree that you need to keep the basics covered. However, CLR/SHM combo has that covered probably 75% of the way as far as HP/AC goes. So streamlining DPS with Wizards is probably your best bet, imo.

Understand that this is per game mechaincs in EQ circa 2004, so if things have changed significantly, all of the above may be complete rubbish.

So, if I were to box 12, the second group would be a full group of wizards, or 5 wizzies and a cleric.

For your group, I'd definitely pick up a shaman, so 5 wizzies and a shaman.

Definitely stay away from bards, as they are incredibly hard to box effectively. They are at their most potent when they are twisting songs, and that is nearly impossible to do with multiboxing.