Well I had to start my 4 C party over as the game kept crasing. Bought
the newer ver. of the game hope this helps. tried to stay as low of levels
as posible but had to go to level 4 as the 8 level rats where too much.
almost done the monistary. going to try and make it to arnika at level 4.

And I ditched the lord I had he was usless I was using him as a priest so I
decide to go with a priest, rouge,fighter and alchemist.

For a 4-person party i've tried, 1-fighter, 1-valkarie,1-gadgeteer,and a bishop. Worked out great. By mid game, my fighter had a triple shot crossbow, and blood lust w/ a shield (bishop very useful at uncurseing bloodlust after each battle), my valkarie had a stun rod (kind of slow but, the enemy can't kill you if they are paralyzed or unconscious)and a blunderbuss, gadgeteer has all his gadgets not to mention a very useful regenerating stone, and the bishop spells, spells and more spells. In summery i had all 4 spell books covered, 2 portals (very useful),& locks & traps.

I never leave my characters at low lvl. I did this a couple of times but I didn't find any difference. Besides, the higher the enemy the more the exp!