Instead of killing the rest of your team for focused levelling, or guarding six turns for full Job Level ups....
You can psychologically build up the endurance AND your team.
How?
Easy.
Go to a dungeon with monsters in sets of three (Like Bahamut's Lair, the cave where you battle Leviathan [which essentially disappears] or the cave under the triangle island....
Have all four characters have different jobs. In battle... have one person attack, the rest will need to Guard. For thieves, use the steal command, don't flee accidentally, this will break your concentration.
This will give you decent gil and reasonable EXP.
You will have to grind. But it won't feel like it. Especially with a thief. You'll steal items such as hi-potions and semi-valuables such as Arctic Winds.
Don't check the character status or job selection screens too often, or you'll realize how long it really is taking.
Doing this, I have only three separate jobs left to master, and I'm starting to let the characters master jobs already mastered (three lvl 99 freelancers).
When all characters have 99 in every job, I'll post in the Mognet thread and give everyone mastery signatures.
Why would I post something as pointless as this? Because this game really is incredibly fun, and too many people lose heart. This game is hardcore.