Sure there is a problem with using RtwP examples but TOEE did just great with larger parties. TOEE had lots of problems but combat wasn't one of them.
Get onto the Solasta forums right now and you will find people discussing how to build characters to replace the thief -- do you build the ranger into the lockpicker / trap disabler or is better to give that to the greenmage? It's a problem I'd rather not deal with. I liked the BG2 party -- lockpicker, meat shield, healer, archer, mage, wildcard.
In a 4 person party I just don't have space for wildcard (sorry bard) and I don't like the building against class strengths -- yeah you can make the bard the trap disabler or have the mage pick locks but that's just not as much fun as having a thief in the party.
To be fair, the 4 party member dynamic with the stock roles does pose an entertaining challenge.
Tank Heal Blaster Lockpick/Trap
One of my favorites if you are into the various subclasses.
Paladin Tank (Oath of Conquest) Druid (Circle of Wildfire) Divine Soul Sorcerer Bard, with thief skills.
Covers everything, and even gets you a little flame pet. This is what I will put together if/when we get to have our own party from the start, depending on if we can add in our own Classes via Mods, I'll replace the druid with a melee/divine class I am writing up for my own setting.