I replayed the OC again recently, after there was a thread that asked whether arcane casters were necessary in the party. My argument was that a rogue with a high Use Magic Device skill could compensate via wands and scrolls, so I decided to put my money where my mouth was.
I built a Halfling rogue / ranger / shadow dancer / shadow thief character who specialised in slings, taking skill focus in UMD early on in the game. He more than compensated for a lack of arcane spellcasters - although I'll admit that having at least one divine caster in the party helped. I was surprised how many wands and scrolls are thrown at the party. I ended up selling a lot of them, as I was acquiring them faster than I could use them. Eventually my Tempertuppin's +5 holy ever-thrower (infinite 1d6 fire bullets, +2d6 magic damage vs evil) proved more effective than any wand or scroll when Improved Rapid Shot was active.
I gave Elanee the Zen Archery feat as early as possible and equipped her with a composite longbow (keeping her out of harms way). I specialised Neeshka in heavy crossbows, having her take Rapid Shot. I tended to take Khelgar along as a meat shield to keep the hordes at bay while the party's archers did their thing, a role he performed admirably. I gave him exotic weapon proficiency, so he usually had a katana or bastard sword, along with a tower shield.
Later in the game I got rid of Neeshka (my character had enough rogue skills) and built Zhaeve as a melee fighter, giving her exotic weapon proficiency as well. The only time I took an arcane caster along was when I had no choice - Grobnar to recover one of the construct components, Sand while looking for plot-related evidence, and Qara to gain a plot-critical scroll. I find all of the arcane casters in the OC to be varying degrees of annoying, so I was glad to be rid of them. I can't quite fathom how Grobnar and Qara can have such high charisma scores, yet manage to be so unlikable. 
And my favourite party member? Probably Khelgar, as he was always up for a fight and kept his whining to a minimum. Unlike many of the other party members who had secret agendas of their own (revealed only if you could be bothered improving your influence with them), Khelgar was up-front about his motivations. In fact he shares his intentions with you from the first moment you meet, without any of that 'secret squirrel' nonsense.