It all stems from what is needed to succeed in an encounter.
DPS, melee, DoTs, DD, DS
Healing, during and between fights
Buffing, too many to list here, choose what is most important
SoW, never leave home without it
Crowd Control, mez, root/snare/fear, off tank
Single pull, lull, FD, mez
So if each player can contribute in multiple areas and cover all the critical areas the group should work.
Pally, Druid, Beastie
Pally decent tank, heal, rez, hp/ac buffs, shines against undead
Druid, heal, travel(SoW, Port, Evac, lev), buffs, DS, snare/root, DoT/DD/AEDD, regen
Beastie, DPS, buffs, slow, pet w/procs, Sow/lev, heals, mana/hp regen
Crowd contol will likely be the issue here, but the pally can lull pull, beastie or pet off tank, druid root or snare kite are the obvious options. Haste is also missing except for pet.
DPS is good, even better if you stick to undead zones.
Healing is covered by all plus the Lay Hands and Rez.
Melee stats will have buffs, brain buffs are limited to the beastie spiritual line.
This would be my prefered group, but I have been in 3 caster groups before that have worked out great, as long as the <cough>tank can stay alive long enough for the nukes to land. Knowing you classes is key to getting the most out of any group.
Edited, Tue Feb 28 16:18:15 2006 by Javious