not properly balanced
IME, that's just the dangers of running Pathfinder. There can be such a disparity between a well built character and someone just going through character creation picking random stuff that it's hard to balance for both possibilities. As a DM, I've always kinda played it by ear and tried to have some way to scale the difficulty on the fly built into as many encounters as I can.
I haven't gotten that far into the game, but I can't imagine how awful that would be with a badly built character if it was a slog with a good one. If it wasn't such a time investment, I'd consider building an intentionally awful party and see how brutal it was lol.