Ouch. Heck of a difficulty curve. First few battles (normal mode) take some getting used to, then things are pretty smooth sailing so long as pay attention. Then about level 15 hit a wall. Regular enemies aren't terrible, but grid you down, and boss monsters are a tank. Shrug off everything you throw at them, and pour out damage, even after you pick off the minions. Specifically Yeon and Security Shimmer stomped me into the floor.
Edit: New Game+ and a better understanding of party mechanics helped to greatly flatten the curve. Later boss battles are harder, but not the same death spike.