This is a stupid post. Are FATEs the fastest way to level? Sure. Do you HAVE to do them? No. I do some FATEs here and there but I've been doing the main story, doing the guildhests, dungeons and some side quests and I'm level 40 with no issues (this game has been out about a week by the way AND a lot of people work full time + school + INSERT TIME CONSUMING LIFE RESPONSIBILITIES HERE)
