I guess the first thing I would say about job evaluations is that, although they did a great job in doing so and really improved alot of jobs, at the end of the game there are just classes that are really good and ones that aren't useful.

First, some of the jobs you talked about:
Warrior - actually a very solid choice anyway you slice it. One thing I did that was interesting my last playthrough was to give him a bow and arrow and put him in the back, early in the game. With a decent bow and arrows, he can deliver a good amount of damage, plus the armor and stamina makes him highly resistent to physical damage. Alot like Barret in VII.

Viking - another good choice, even higher defense than a warrior, and still gets some solid weapons end game, though it doesn't compare to the later ones i'll get into.

Dark Knight - probably one of the best jobs in the game, because of the fact that it can dual wield Ragnarok and Masamune. I don't think I need to go beyond that.

Knight - possibly the best fighting class in the game because it can equip crystal armor, and Excalibur and Ragnarok.

Dragoon - it seems a few people have overlooked this compared to the ninja or knight. You can get 2 sets of Crystal armor endgame, so the dragoon is already ahead of many classes. But with the Holy and Dragon lances, this job really rivals the Knight.

Bard - this is where we get to what i was talking about earlier. Seeing how bards usually get trashed on in FF, I wanted to see how I could make use of one in III, and they are very useful for a good part of the game. Madhura Harp allows you to cast protect on all characters, although the white mage can only cast one at a time. Loki Harp casts haste on all, as the white mage can only cast 1 at a time here too. Dream Harp restores an ok amount of HP to everyone, but you have to level up the job to get it decent. Also, none of this uses MP, so in a lot of ways, the bard is better thant he white mage.

And then there's the Lamia Harp. I don't know how many people know this, but I think this harp's song deals 9999 damage against all enemies in the Final Battle usually it deals miniscule damage, decent to undead, but when I played the final boss the first time around (don't want to spoil this) it dealed 9999 to all enemies.

The only problem is the Bard doesn't have what it takes to push you through the endgame. Even at high levels, dream harp isn't reliable as a healing source. The songs are ok, but you're really better off having a devout, who can cast a wider number of spells and full heal and full life at will. The bard has to use phoenix downs to revive, and this won't cut it in the endgame.

The Geomancer has the same fate. Don't get me wrong, this job will get you through most of the game - the spells are usually just as, if not more powerful than a Black Mage's, and even though it's random, there's only at most 3 enemies at a time, so it almost always works in your favor. The fact that it doesn't consume MP makes this job alot better than the Black Mage. But in the final battle, you really want to be able to control who is targeted with the magic, so the magus/sage/summoner all block this class out.

the jobs of ninja/knight/dark knight/sage/summoner/devout/magus/and dragoon are all superior to the rest of the job system in their sheer usefulness. I think they really did a great job in balancing the jobs out, but they just didn't quite get there. maybe with the moogle sidequests, but i have yet to do those.

One class that I will say has been greatly improved is the Scholar. Despite using magic, once you get the scholar robe and hat, this really is a melee character. The damage it can put out from books is stunning, especially as you gain job levels. I think in a side dungeon you can get a book which does a lot of damage. Plus this job can double the use of items, so high potions and spell items become that much more effective. Add in sight and you have an all around great job. I don't know about endgame though.

Just some of my thoughts, I know there's alot more to get into.