Their stats will rise as their job levels go up so don't worry, though you should keep the monk unarmed cause that is a classic FF secret. Red Mages are easily the most broken class in the beginning of the game. Warriors are good until your Monk gets a few job levels then they will easily overtake the Warrior in terms of damage and Hp gain. White Mages and Black Mages are good stand-by's. Thieves are pretty much useless in this game until their Job level is in the 70-80 range. Course the only thing you need them for is stealing elixirs from Dragons at the end of the game and stealing Gungnir from a certain boss.

The characters are a bit like the FFV party imo concerning stats, by this I mean you have one character geared towards magic (Lenna/Arc), one towards physical(Bartz/Luneth), and the last two are more in the middle though each does slightly move to one side of the damage equation. Faris and Ingus are pretty good with magic but seem slightly better at physical while Krile and Refia are good physical fighters but seem slightly better with magic. This is just my view and it may be eschewed by my warped bias.

The only classes I don't care for are:

Rangers - costly and you have way better options that outweigh this classes advantages.

Scholar - Really bad for completionists, Great with magic, crappy MP, terrible Hp growth. They are powerful but it takes a bit of planning and once again it requires stocking and hording magic items.

Evokers - Just no... Use a Geomancer instead and wait for the Summoner class to open up.

Still, its mostly up to you on how you use them. Also, a bit of friendly advice. Save often and try to use the Phoenix Downs sparingly. You cannot buy these, you can only get them from treasure chests and as a rare drop from monsters. "Raise" is the reason why White Mages stay useful to your party for a very long time in this game.