and as you all know. the final stages of the game are designed to let you master all of the classes pretty easily. and of course the magic urns.
unless your a perfectionist, you should only want to be on a high level or just have people who are good in a couple of job classes.
to beat the final boss i used,
one person with high health and summon.
another with summon and time magic.
and two with summon and white magic. magic is my best friend!
neo-X-death went down pretty easily after that. i'd lost a lot of times before on about level 43 or 42 and i was able to win by simply changing my job classes around so its really not neccasary to master them all unless going for harder bosses. in that case you may just want to master a few and go to bare job class so that everyone has high stats and good skills.