My party setup

[ReloadPsi]

Right now: Knight, Master, Red Wizard, White Wizard (Done class change, yay!)

Normally I prefer two Fighters and two Red Mages. Easiest party to use if you overlook how expensive they are; they can all equip decent weapons and the Red Mages have a better armour selection than their more specialised counterparts, plus they don't stand in the back row hitting for slightly-above-zero damage while you conserve the spells for more dire situations.

I never, ever take a Black Mage except for "novelty" value (and by "novelty" I mean "extreme frustration", or maybe I mean "novelty" in sense of "joke" rather than "fun") and it's extremely rare that I play without a Red Mage (or Fighter for that matter) as it's my favourite class... but my "usual" setup indicates them as being my constant :P

Thieves are incredibly broken in DoS; they get 2 hits per attack right off the bat for me and once they gain the ability to cast FAST/Haste and Temper on themselves after the class change you might as well consider the game beaten. Red Mages can, of course, cast Haste and Temper on themselves as well.