Since the premise was core-only (and hurrah for that).......
Dwarf Wizard X (probably specialist conjurer or abjurer; conjuration covers just about everything evocation does, anyway) - high Int, high Con, good or decent Dex, everything else = dump stats; spend most of his cash and spare time on scribing new spells and scrolls, a spell or three for every situation; take feats like combat casting, one or a few copies of toughness, improved familiar, improved counterspell, still spell, silent spell, spell mastery, and perhaps one or a few copies of spell focus; knowledge skills like arcana, architecture and engineering, history, geography, and the planes; good concentration and spellcraft skills; could be cool to roleplay, would be fairly resilient, could have a tough and capable familiar, could be the group's sage, and would always have a few spells prepared (stilled and silent) by memory that could get him out of a bind (Animate Rope, Mage Hand, Shatter, Sleep, whatever).
Human Barbarian X/Fighter 2 - high Str and Con, and perhaps good Int so he could have plenty of survival/scouting/travel skills; probably focus feats on track, power attack, cleave, improved sunder, improved unarmed strike, improved grapple, and iron will; can be an effective caster-killer with his speed and improved grapple (I don't care about your Shield and Mage Armor, puny mage! I grab your head and crush you!); will need a bow sometimes, but won't rely on it most of the time; could be interesting to roleplay with a good mental ability score, grappling prowess, strong willpower, and scouting skills.
Halfling Rogue X/Fighter 2 - high Dex and Con, good Int and/or Wis as secondary focus; could scout with or separate from the barbarian, and could tank alongside him too with good AC/HP; rely on sneak attacks, primarily through flanking, for damage-dealing, so Str can be low; feats focused on stuff like dodge, mobility, weapon finesse, spring attack, and improved feint (and whatever the feat was that it requires, don't recall if it's combat expertise or combat reflexes); skills emphasizing sneaking, traps/locks, scouting, and travel, with any extra points going into knowledge - local and one or two social skills, namely bluff and either diplomacy or sense motive; a bow would be essential for some situations, though best used from short-range after an ally has paraylzed, stunned, or unbalanced a foe somehow.
Human Druid X - high Wis and Con, secondary focus on Dex and Int, relying on wild shapes to gain high Str for melee when needed (can probably wield a scimitar in ape form anyway!); skills focused on effective magic-use (concentration, knowledge-nature, spellcraft, etc.), animal handling, and general utility, but movement skills won't need any more increases when Wild Shape kicks in; feats would focus on point blank shot, far shot, track, combat expertise, improved trip, lightning reflexes, and the feat that allows spellcasting in Wild Shapes (name escapes me at the moment); druids can be pretty versatile, and since they can be pretty strong on the offensive, they won't really need to heal allies as often since the group will be wasting enemies at a good pace; an animal companion can make a useful support tank, and this group will be pretty devastating in melee.
Gnome Bard X - high Cha and Int, good Dex and decent Str; the group's "face," enchanter, and ranged combat support; feats emphasizing skill use, spell DCs, crafting potions or something, and especially ranged combat; resident master of the bow, using bull's strength and such to make effective use of composite bows; great support for the group in general, and could probably have the skills and spells to be a fun trickster and the comedic relief.
