IF you are referring to Coil well my dear that is a different thing. The binding Coil of bahamut which has an i70 requirement is endgame and you get a 15% echo boost in there now making it stupid easy. coil is ENDGAME not main story(though related and great story). Also there are 2 duty roulettes that you can do, hard mode and trials which give you an extra chunk of myth for just doing 1 dungeon/fight a day, Trials rarely take over 20min and dungeons rarely over 40. A lot of people don't grind dungeons repeatedly, and they get there myth slower, it's a trade off.