True, this game is not much of a challenge fight-wise. Balance is actually worse compared to some of their older games where you were actually fighting up to 3 mobs at the same time and stun wasn't sure effect (actually there was miss chance for any attack) or wasn't a skill at all.
While it still wasn't much of a challenge you actually had to think during fight instead of just rollballing through any enemy otherwise you can die easily. I think they decided to focus more on H on this one, reducing the time the player will spent on fight/grind.
The only reason to stay in a fight is actually for h anim and gaining a lvl here and there.
For the same type of story (corruption, normal/whore-slave/evil road) and same battle with more difficulty I'd recommand trying "the heiress" , "dark elf historia" or "killing time". Same devs. Only weak points of these games is that while fighting is better, global quality is worse, be it traduction, bugs, cg/anim quality and diversity.