Well the thing is that if you defeat optional bosses and then go on to fight the last boss chances are you´re already way overpowered and most likely you can defeat them with ease!
FFVI is no exception i actually found Kefka to be one of the longest final bosses of the FF titles that i have already played it´s not so much that his hard but the different forms/towers that you have to face that make him a cool boss!
