My advice isn't that you need to level up more, but that you need to master some more jobs - especially to recieve the innate abilities that come with mastering a job. (For example, mastering the ninja job allows your character, when bare, to equip two weapons - an extreamly useful ability.) Because you have so few mastered, you're unable to combine abilities - such as Faris being unable to wear armor because she only knows mage jobs. You don't have to be a freak like me and master every job for every character (although I must say it gives you many strategies to choose from ) but a few more would be helpful.

For starters, finish up those jobs you're close to done with - let Bartz master knight, faris master black mage, and Reina master Ninja. The area right before you meet Ex-Death is great for gaining AP - you usually get about 30 a fight, and encountering the movers gives you 150. You should have those jobs done in no time. I wouldn't worry about Krile's Blue mage job - its a helpful skill earlier in the game, but it does little against Ex-Death. Instead, a highly recommend having Krile learn the Dancer job. Although at first it does nothing, once she learns the dance ability, it comes in highly useful: her jitterbug dance steals a lot of the enemy's HP and gives it to you, wonderwaltz steals lots of the enemy's MP and gives it to you (both these are great when training and you're running low on tents and cottages) while the ultimate dance, sword dance, does a lot of damage, especially when she's holding a big weapon (and since Krile has mastered the Samurai job, she'll be able to sword dance with a kantana - sweet!) This ability works well on Ex-Death. Finally, mastering that job allows you to equip a ribbon, which protects you from all the negitive status effects Neo Ex-Death throws at you.