FormerlyHemlock
Hero
So, is it time to point to this again?
I'm not sure you can actually ruin a character with multiclassing unless you find some strange esoterc anti-synergy to exploit. I would certainly play the every-class trope, if it fit a game. It would be interesting at the very least.
That character is indeed pretty terrible. It might be possible to make a worse one, but that PC is probably 50% worse than a single-classed PC, due to anti-synergies and MADness.