I guess it's pointless now that there's an easy mode, but when I found the going quite tough late in the game back in my first playthrough in 2011, my eventual solution, which carried me through all the way passed the final boss, was to kit out my party with as many high grade evasion gems as I could, so that the enemies basically couldn't touch me.
Probably not the most efficient solution, but I was an RPG noob and found the in-depth stuff a bit too daunting. XD