I found a bug. If you reset your data, all of your weapons and armor in the museum will still be there until you take one of them, then they all disappear,but you keep the item you took. This demolishes most of the difficulty.
Big tip, don't neglect your elemental resistances. Regular defense doesn't protect you from them at all. For example, and enemy with 100 attack and 15 fire attack hitting a player with 150 defense and 0 fire defense would do 15 damage.