A NG+ run with the extra boss seed on Dark Val would indeed wreck everything with him as CPU lol

With just freeze boost, the chances are 50% already, all the stacking is additive so it's actually better to augment it with petrify and have an additional 35% chance of instant death to regular enemies. Palamena's wind class passive also provides a global 20% to every status effect inflict rate.

Sounds something that might be worth to try if they ever add some a harder NG+ only difficulty or level reset. Sadly there is very little point in playing the NG+ at the moment, since Expert difficulty seems only useful for clean new game plays and gives no challenge to max level characters.

I think that builds don't really matter that much for main story. First skill upgrades are cheap anyway, you can't get last upgrades until very late in the game, can reset points by then and at that point end-game trash monsters die almost instantly anyway using shield. Unless using speedrun low level strategies, boss focused builds might be more useful after post-game unlocks.