I also don't see this as op because despite it always being up only sch and white mages have the ability to shield and heal the whole party at any given time save CU which you have to be immobile for and isnt a global cooldown anyway. They would shine in juggling if they want to put the sun and moon on two different ppl while using synastry on another two or concentrating on let's say someone just got weakness and instead of spreading out your assets you put the sun and moon on that one person for increased concentrated safety while sacrificing your control of more even mitigation