If you want to beat Yans easily just equip Dagger with boost and Use Atomos, then use climhazard with Steiner

Ozma is a VERY tough Boss... which means... I do have my very own walkthrough upon his defeat if you should need it. its very thorough.
and if you have noticed, it is immune to every status effect in the book!
and you only get 1 attack in because of Ozmas Speed range.
I use 2 methods in this All-out war: the "Magic Hammer" method, and the defensive method (taking both white mages with you and having auto regen and auto potion[hope you took the time to buy 99 Elixers] and discard potions and hi potions. need more help just ask me