For six PCs, lets go for one of each stat as primary:

Str: Fighter, Half-orc, using a 2h weapon
Con: Warlock, Genasi, infernal pact
Dex: Rogue, Drow for edginess and because cloud of darkness is just that good
Int: Wizard, Pixie
Wis: Cleric, Dwarf, ranged build
Cha: Paladin, Half-elf, using a sword and shield

Skills will certainly be covered well. You've got three melee and three ranged, though both strikers can switch.