In essence, Mr. Oldmanpaco, what Desiderius is trying to say is that P:K is very similar to BG 1/2, in the sense that 3 classes are for character that you ought to solo with (or maybe 1 other char).
2 classes are for the people that know what they're doing. Or banking on a very good gimmick a la Jaheira Harm shenanigans.
And, generally, you ought to keep it to pure classes.
The only one that is a blatant disregard to that is Octavia, but she's easy to be explained if you jog that gray matter a bit.
But it has a similar issue to the BG games, where (later on) the game is easier solo, mostly because those other party members die easily and your PC is unhittable.
I always play with a party but some later areas are made easier by parking everyone else at the entrance.
You’re doing it wrong. Really wrong. The game is all about team design and working together tactically and strategically.
Does your entire party have unhittable AC or something?
E.g. Pitax palace was much easier to clear with just one character, buffed up by the party.
The AI in general is not smart enough to change target on the fly. Just position your party in such a way that put attention to your "tank" first. They even rarely try to attack your ranged party member. If your melee damage dealer is getting hit everytime then you kinda have shit positioning.
With full party the enemies should also die like several times faster unless you messed up somewhere and not hitting them.
In the case they do get hit by something, the game should more than provide enough tools to survive, especially
in Pitax of all places where you are nearly on demigod level. KM has a reverse difficulty curve that the game actually becomes easier with time on fixed difficulty due to how strong your party is. If you feel it is easier to solo clear a dungeon because your team keep dying there is probably issue with your items, not using your spells to protect the party, or you really2 botched up feat selection or something, or possibly you have really2 terrible positioning or you play this game like RTS where you just block all character and right click or something,