Uhh... Yan Angwa (what sucks about him? he seems fine), Myst, Midian, Deus, and Orlando? They seem like the ones with high enough MAG scores to be considered primarily mages. The way magic works sort of puts me off focusing on it. Ought I do so, then? Blerg the current top-level of spells are so absurdly expensive.
Carson and Griever are pretty rad fighter-types. But I guess those aren't worth bothering with?
IIRC, when they're at the same level, Yan Angwa has the lowest MAG of any of the mages you have. I was using Myst-Midian-Deus at that point, then swapped Midian for Orlando when he became available. Myst and Deus stayed in my party through the final battle.
At least two fighters are worth bothering with. I used Jovian when available, and at the point you're at Bast, but the non-Jovians fighters you have should be pretty interchangeable, so just take your favorites. For a long time I used... Derek? The skeleton you get with Myst. Anyway, used him as a third fighter and often went without Daniel in the active party. Derek is a great tank. So three fighters is by no means a bad idea at this point, especially since Jovian is equivalent to a mage in single target damage until the late-late game. Four is DEFINITELY overkill, and even three is pushing it if you have Daniel in the active party.
The biggest problem with fighters is actually the expense - mages are much cheaper. Keeping ALL your mages in top level spells costs about the same as keeping one fighter with a fully upgraded weapon, and the best fighters (JOVIAN) pop in and out of the party at times, which makes all your investment worthless until they return. By contrast, every mage you have benefits from the spells (albeit some are, obviously, weaker than others). This is important at the stage you're at, and will only get more so as you go on - especially when you have to make multiple parties and use fighters with largely unupgraded weapons.
By the endgame the mages drastically outdamage the fighters, as well (the only way fighters can keep up is when... buffed by mages. >_<) It's rather like 3e D&D in this respect, except fighters CAN actually tank (and mages actually need them to).
Also, are you swapping characters in battle? Some of the status effects (Freeze!) make this very important.
ALSO also, I had a thief in the active party the whole way through unless I was either in a dungeon with nothing worth stealing or where I needed a fully-kitted-out combat force just to survive randoms. Having and aggressively using a thief makes a big difference money-wise. (Handily, you'll fairly soon be able to get a character who is both the best thief and best mage in the game, so this becomes no question at all. ^_^)