I'm playing Thief/White Mage/Black Belt/Black Belt right now - my "unpopular party". I can tell you, it is the first time I try it without everyone's favourite sword-lover, and it is a challenge. No armour, so I have to put the Thief in the front row (has slightly more HP than the others at the start) and cast Invis on him in almost every battle. Of course, the lack of shiny swords is also a problem. The Thief is a runner, not a fighter. The White Mage doesn't like to hurt anyone, and the Black Belts are just starting to do any damage now, on level 9 and 10. I started exploring the Marsh Cave, but had to turn back after two floors because I ran out of spells (and Thiefs).
On the other hand, this party will probably get very strong after class change, if they survive that long. I can't even survive near Pravoka Fingertip at my current level - Giants squash me like bugs.