|Benicio Del Espada|
I'll go ya one better! We played a home PFS session with all Arcane casters, and it was quite balanced. Had the two who joined later continued the theme, we could have been a powerful party.
We had Summoner (DM to fill out 4)
Melee focused Witch (with healing hex and CLW)
Evoker wizard (who was playing a tomb raider stealthy wizard)
and myself a Bard (Magician archetype) (also had CLW)
Had we continued with all those chars, we could have still added: Alchemist, Magus, Sorc, or a different wiz/bard/witch/summoner.
The two others that joined didn't believe that an all arcane group would work (even though we found it worked quite well). I would have loved to have tried it longer. Ah well.
I tried this once. Two blaster clerics, one wizard and one bard.
IRL, the bard was stoned, the wizard was bipolar, and the GM was attention-needy. The clerics (one of whom was me) both tried to play it straight, but the game collapsed after the wizard spent half an hour transfixed by a nearby thunderstorm and the GM decided to "get some air" in said storm.
Most awkward game ever.
Still, being a Death domain cleric in a party with overlapping channel negatives is a hoot.
Try a Core Rulebook cleric, druid, sorcerer/draconic disciple, wizard party...
Or a bard, cleric (Animal domain, take the Boon Companion feat), druid, summoner and bury your opponents in pets and summoned creatures (buffed by the bard)...
You could even go with an all arcane or all divine group. Alchemists, bards, and witches can act as healers on the arcane side, while clerics (with the right domain choices), druids, and or oracles can act as blasters/battelfield controllers.
At low levels, you need to watch spell slots and know when to "fight another day" (when your spells are renewed). Once you hit 5th-6th level, you should be able to handle most situations fairly easily.
Now, I hate the 'slot' tropes, but they are necessarily, to some degree, in any party, as we all can't be the fragile Wizard (God) in the back without somebody up front to take a smite or three to the face.
So the 'Bulk' for a 4-man caster party? Bard with the Armored Caster feat from 3.5 to allow medium-armor wearing without spell failure, or a bard with the full +5 Chainshirt and +5 Light or Heavy Shield can make a tolerable tank, especially if the rest of the party throws him some love.
The Alternatives are also a Wildshaping-focused Druid and her pet, or a Summoner with a defensively-minded Eidolon. Druid has the benefit of being able to turn into a similar monster and tag-team the enemy with impunity, while the Summoner has the advantage of being able to pull the 'big guns' out of nowhere, given 10 rounds or one minute, whichever comes first!
For the 'Hiroshima' guy, a Sorcerer or Wizard can pull this off nicely. Witch, less so, but given the right Patron, could still be tolerably effective. If Fireballs are the name of your game, focus on giving the rest of the party some protection first, but this applies to any Elemental Spell you're going to be tossing around to spread the love/pain/agony/death/fear.
As the 'McGuyver' guy, a Wizard, a Witch or a Bard comes in handy. Bards generally top this list, having a rather unusual spell-casting list, but a illusion-loving Witch, or a Wizard dedicated to traps, golems and other humanoid-crafted wonders can also fill the role. Use summoned monsters to spring traps if Disable Device is not available, Illusions can make it look like you have an army of Mooks waiting for the order to go crack some skulls, having a few Tin Golems running around building things for you is always handy.