Actually, I found out why I thought the game was so easy…. I don't die often, but on a few hard fights I did and pressed on retry and won them… in the last chapter I finally realized, that each time you press retry the fight will get easier.
So it doesn't matter on what difficulty you play, as the battles gets easier on each retry until you win them
I felt a bit stupid after noticing this… I know some other JRPG's has this mechanic but I didn't know such an old game would have it, so I was kind of surprised. Since these games are mostly about the story though, and not that much about the gameplay I don't mind so much, it is actually quite convenient to know that if you fail on first try, you'll win the fight on the second one.
If this was something like Ogre Tactics though… then that kind of mechanics would really piss me off.