Since I got basically no experience with DnD or PF, I’ve used build guides for my playthrough, so I’d like to think they were well built.
As I’ve written in another post, the last third of the game was just a complete slog, with overtuned enemies, that took far too long to kill.
I did play on core difficulty (“intended PF experience” or something), but as far as I can tell nothing affects the enemy HP, just how much damage you take (maybe there’s something in the custom modifiers). I guess even with a weak character you can get through on a lower difficulty, but it’ll take ages.
However, even if I used proper builds, I still used my very limited knowledge of these games and systems. If you know what you’re doing, you can probably use better spells or abilities to kill things faster.