I also loved Tales of Phantasia, and I played it a lot on the Game Boy Advance, after passing that installment, I had researched and found out that the game has a saga, they are all “Tales” so it was great for me to play all the installments I could, and this game has been on my list for a while, only my computer doesn't support it yet, but it's an amazing video game from what I've seen in some videos.
But from what I read in your post, it's a shame that in terms of difficulty there isn't much difference....
Do the enemies even cause more damage ?
They probably deal more damage but it wasn't really noticeable. The game isn't bad, it just doesn't suit me very well.