I'm having the same problem as Bananamama, the first boss, Rocky, in the 4th level of the desert is likely broken. All enemies up until there had 90-500hp, this guy has 270.000.
His move-bar fills up to lvl 5 before mine reaches lvl 1, so he definitely always has the first hit, dealing over 2.000.000 dmg to my party, which, even after grinding for 1h are only around 1.500hp.
I tried reloading the game to "fix" the issue, but it keeps happening. This guy can't be skipped either, there are no conversation options to avoid the fight and the entire stage can't be skipped. It's also none of those fake bosses that are supposed to be unbeatable, because after losing I just return to the map. No conversation afterwards, no other level unlocked, nothing else unlocked to defeat this guy or have him join my team.
So either I'm supposed to grind for weeks on those low lvl desert monsters to eventually build my team up to defeat this dude, OR he isn't supposed to be anywhere near as strong and the game bugged out, maybe caused by the NG player.
Anyway, the game can't be played beyond that point, and all medals on here are tied to mid- or endgame stuff, so they're impossible to unlock either.
Until this gets fixed, the game is just a waste of time for everyone who's playing for the story or hunting for medals. I spent a solid 3h on this for nothing.
Kinda sad though, the game looks promising...