I never played 4 Heroes of Light. How similar is Bravely Default to it? I looked at a trailer for 4 Heroes and the 4 main characters look awfully a lot like the 4 main characters of Bravely Default.
I'm about 55 hours in in Bravely Default on hard and at level 60, and I'm only on chapter 3. I think the biggest default with Bravely Default so far is that you have to constantly grind (for hours and hours). The game isn't hard. It just is impossible if you don't grind to increase your levels.
I might turn down the difficulty before I end up losing interest.