I skipped a lot of the endgame with my Four Job Fiesta party. I couldn't make use of more than three of the legendary weapons so I didn't bother acquiring them. Instead I just grinded a few levels and headed straight for the Void.
The Void had a couple of really awful fights. In particular Calofisteri - translated elsewhere as "WoodSprite" - was a problem for my damage challenged party of Thief, Red Mage, Beastmaster, Chemist. It's possible I could have killed her with four Release commands before the battle even really started, but I wasn't preloading for every battle, and wanted to win without having to try again if possible. The big challenge she presents is counter-attacking with Drain every time she is attacked, and putting Old on characters. There seems to be a bug that leaves you very weak if you remove the old condition from characters, so I was left in a position of being unable to hurt her. My road to victory was to wait until her 1000 magic points ran out and then very slowly race her Regen.
Twintania was also a bit of a problem. I think I might have been able to Toad it when it was charging gigaflare, but I beat it with four Reflect Rings and it's own magic counter attack.
Necrophobe was basically totally out of the question. Again, probably I should have just used Catch and Release to obliterate him, but he's optional so instead I just left him alone.
Now Neo Exdeath is quite a final boss. His grand plan is to use the power of the void to unmake everything that is and then he too will disappear forever. As motivations go, I suppose it make about as much sense as anything else. He's got four segments that take individual actions which do a lot of bad things to you, and when you get him down to his last segment he goes a bit nuts and starts casting Meteor on you. Again, he's a problem if your damage is terrible, and this time Release doesn't appear to be a silver bullet.
Fortunately the chemist comes to the rescue. Chemists can put all kinds of weird status conditions on you, many of which persist through death. Chemists can mark you as a boss making you immune to the majority of status conditions. They can give you absorb lightning, fire and ice. They can increase your level, increase your magic damage by 50%, and double your maximum health. They can also resurrect characters to full health and magic and do full heals of living characters using extremely cheap mixes. Resurrection to full health and mana is Phoenix Down + Potion.
With all of these buffs I could ignore Neo Exdeaths most threatening ability, get healed by his occasional elemental spell that would otherwise do huge damage, and force him to kill me again and again and again until I finally ran out his health.
All in all, though, I wouldn't say I loved the four job fiesta. In a way it's nice to participate, but what I like about the job system is being able to do all kinds of interesting things. The four job fiesta forces you to find the one thing your combination does well and use it to beat every fight.
Anyway, I'm done, so I've started a new game where I will learn all the blue magic like I'm supposed to.