All I'll say is 'get used to it'.

You have a huge range of powerful options at your disposal in battle as the game goes on, and if you play the game well you don't need to level to beat most any boss. But unfortunately playing the game well generally demands that you have prior knowledge of a boss's capabilities. Which means getting curb-stomped at least once.

The difficulty level isn't unfair, but it's pretty darn ruthless.

I don't know how much harder it gets after the 20-25 hour mark, but I'm pretty sure I picked up more game overs in its first half than in any RPG I've played since like...uh... I don't even remember.
Undub, I take it? Or are you actually enduring that...thing?

That being said, I suppose the undub might be disadvantageous if you don't speak Japanese, as the things your characters say at the start of each round give you big clues as to how a boss is going to attack that turn. Can't remember exactly what the line was for a really big attack, but I'm pretty sure it was some variant on 'iya na yokan ga suru' (I've got a bad feeling about this). Listen for that at the start of a round, and when it comes up in later boss fights, prepare for the worst. :'D
Oh, and trying to avoid spoilers, but in the dungeon where your party gets cut in half, get as much earth protection for L'Arc's party as you can. You'll thank me later. The boss isn't that much harder than any of the others, but there's no save point before the boss of that dungeon, meaning that dying forces you to repeat the whole dungeon. And all my characters got petrified on the first round, giving me an instant game over. XD That was the one time the game really crossed into masochistic territory for me.