Guess what? I just beat Fantasy Life's main story without much effort. All of the story-only fights are laughably easy, especially if you've leveled up quite a lot. I wonder how hard the story fights would be if I were around Level 10 or lower. I can definitely see it's possible to avoid every non-story enemy just to proceed the story faster. But still, it's worth doing the main story because you'd gain quite a generous amount of EXP, Happy Points and money, along with unlocking every area.
Even after the credits rolled in, I've got plenty of things to do, such as more happiness quests, jobs to complete, purchase all of the villas, and whatnot.