Well, I didn't feel too easy when I fought them for the first time. But I agree the game's difficulty is below average, especially when you know the system well enough, it becomes a piece of cake. Fairly low difficulty is good for those who wants to enjoy the story during the first play through, but not for those who like challenges.
I recall when I fought Miguel, I tried about ten times before eventually won(too bad you have to read his preach every time you suffer a defeat). Garai, Dario, Polis, etc, Police all caused troubles. Some regular enemies are actually though when you fight them for the first time. IIRC, the Viper Manor mission is tougher when you choose Pierre's route, though I only tried that once.
I guess that was because the characters are not well equipped and I didn't know the patterns of the enemies quite well. For example, Miguel killed Lynx in 1 hit at the beginning, which is quite annoying consider I didn't have any Revive element.