Freelancer: 10/10. Best physical job overall (though Mime honestly can be more broken - yay 1 turn dead Omega Mk II!), though requires you mastering other classes first. Still, overall best stats, etc.
Black Mage: 6.4/10. Black Mage is awesome, but overshadowed by many other classes. Still, always helpful, and you can pull some cool tricks with mass Reflect on the team (lol Gogo vs. 2x damage Firagas)
Blue Mage: 8.3/10. You only need a couple Blue spells to maul the game, and they're not too tough to get. Other stuff is situational. Equipment options are awesome - shields, rods, swords, etc. It's a good base overall.
Knight: 5.7/10. The class itself is average, but it's support skills are great - Two-Handed for damage, and Cover/Guard are excellent for trick strategies (lol Gil Turtle)
Monk: 2.3/10. Uh...eh. Bonus HP is ok. Honestly, kind of pathetic, really - the damage trails badly after world 1 (and even during then), although you can use the strength boost of Barehanded with other classes. Once Kaiser Knuckles are available...eh. You'd rather have Hermes Sandals. Good for mastery, honestly, and that's about it. Will kill Jackanapes early, at least!!!
Thief: 6.4/10. Stealing, dashing, excellent speed, Flee, immunity to surprise attacks...yeah. I like the whole support structure here - stealing gets lots of good stuff early to help other classes. The class itself isn't awful to put support skills on - the speed allows you to make good use of, say, summon, or white magic for support.
White Mage: 6/10. The class as a whole is kind of weak, but the skillset is awesome (and Sage's Staff is excellent). Ok for boosted Titan with the Gaia Gear. Mmm...yeah, this feels fair - the tricks are nice, but the class itself feels weak until you get certain key points (Holy, different spells, etc.)
Berserker: 1.5/10. Uh...lots of durability. And has decent damage! Loves Two-Handed! Also, another one to kill early Jackanapes!! Yeah, bad overall.
Mystic Knight: 4.6/10. Not good for randoms. Good for some bosses (optionals particularly), and the stats are good. But...eh. Easily done without.
Red Mage: 4/10. Early is great...but just doesn't cut it after that. Needs another skillset added to it to get it's mastery fairly easily. X-Magic is good...but it is somewhat limiting (best with a Mime so you get 2 full magic skillsets). Just...eh. Other stuff is far better than X-Magic overall, so I don't give much credit to it.
Summoner: 9.7/10. Semi-slow start, but demolishes everything. This is the reason why people miss a lot of broken stuff - Summoner is straightforward and easy, so you rarely need to look for the broken >_>
Time Mage: 8.3/10. Weak early game - really, really weak. Needs another skillset like Black to deal damage, but the skillset overall is great. Quick is badass, and Meteo is awesome against single targets. The status is always helpful.
Beastmaster: 6.9/10. Catch and Control are awesome - takes a bit to get, but worth it on big enemies. Yay 9999 damage early in the game! Demolishes things. Also, some of the whips are nice (Firebute is a nice part of cheaping out Shinryuu).
Geomancer: 2.8/10. Terrain is good...but random. On the plus side, it masters fast...and the passives are helpful. But...blah. Rarely worth it.
Ninja: 8.3/10. Awesomeness. Demolishes randoms. Hurts bosses. Is fast. Great masteries. Durability is a little weak, but...who cares.
Bard: 5.5/10. Requiem alone puts Bard high - it eats up Gil Turtle and Moore Pyramid. Overall kind of weak outside of that one skill, but...it really is awesome. Oh, and Romeo's Ballad on Omega for hilarity.
Ranger: 5.5/10. The mastery is all you want from this class, but it's an awesome mastery.
Chemist: 8.3/10. Requires experimentation, but holy shit...so good. Only source of water-boosting in the game. Great crazy tricks (hey, let's kill a magic pot! Turn it into a dragon, raise Butz's level to max, X-Fight with Dragon Lances = gg). Everything is fairly easy to come by as well, so it's not a class that's hard to keep going.
Dancer: 3.2/10. I...yeah. The equipment is the best part of the job. Sword Dance is nice, but...you can't put the Dancer up front. Just not durable enough, as I found out in my run. Works ok stat-wise with other skillsets, but...yeah.
Dragoon: 2.3/10. lol. Jump has uses, though situational, and theoretically, Lancet is good. Just...yeah. No point, honestly - if you got it far earlier, maybe. May honestly be worse than Berserker.
Samurai: 6.1/10. Mmm...slowish. But the skills are nice. Samurai swords are badass - Masamune kicks ass, and the critical hit rates are awesome. Durable too. And Giltoss is amazing, though costly - trivializes randoms overall, even in the bonus dungeon. Consistent damage is helpful, at least.
Mime: 10/10. Best magical job overall, also decent on physicals (full power Chicken Knife is awesome).
Canoneer: 2.4/10. Combine would be great if you got the job in World 1. Open Fire...has some uses. Equipment and stats are good. Just...yeah. Pointless.
Gladiator: 3.1/10. Probably better than Knight overall...if only it came earlier. Stats are great - mastering it gives you overall great stats in all categories, and if you have to master one class for stats, this would be it. Its skills are good too! Bladeblitz is helpful, though again, late. Finisher is nice, with great average damage. Very good class, just too late.
Oracle: 1.3/10. BEST MAGIC. Uh...everything else is sucky. Really, really sucky. Not worth it, really.
Necromancer: 1.1/10. A neat class, but...wow. No point. No. Freaking. Point.