A single mistake? Sure. But one thing i learned playing WOTR is that you might think you are making the right choice, but you can't actually finish the game with your build.
Oh please I finished WotR with several unoptimized and "badly" build characters, including one which was build from level 1 for combat in gold dragon form (already a suboptimal choice) instead of using respec, meaning for 3/4 of the game all of his feats were useless. On normal difficulty.
Core difficulty here, I was stupid enough to start my first PF game at this difficulty and hit a wall somewhere in act 2. Thank god respec was bugged to be free back then else I wouldn't be able to progress further. But to be fair you can't mess a character this badly in DnD5e.
I also started on core. That character had no exotic builds but also wasn't optimized either and I had to leave several encounters for later like playful darkness. Still finished the game.
