It has a rough beginning but drops off eventually.
You in all probability will get killed several times in the first dungeon. However, once you die the 2nd time, it will unlock the easy mode option (and you can then switch between easy and normal at any time).
I have only played on normal myself (I didn't use easy even though it was unlocked for me), so I cannot comment on how much easier the easy mode is.
You can also save your game basically anywhere, which means you are never going to lose significant amounts of progress just because you died (unless you were being grossly negligent about not saving often).
Even if you forget to save your game and get killed, the game will let you pay with your character's in-game money or with your 3DS PlayCoins (which you get from walking around with the 3DS while the 3DS is in sleep mode) to get revived and returned to where you were just before you died without incurring a game over.
So its a rough beginning, but save-anywhere, the option of easy mode, and the ability to be revived without getting a game-over as long as you pay with your character's money or PlayCoins give you plenty of tools to take it on without becoming overly frustrated.
If you really find this game is kicking your behind, try the three grinding DLC quests, which are around $6 each(?). They make grinding far less tedious, but the temptation to abuse them runs the risk of sucking the challenge (and possibly the fun) out of the game.
Everyone just be quiet and have fun. 3DS FC - 0275-8277-1122