Just wondering, I looked around and coulldnt find much. How much does putting shaman and barbarians into your party affect your karma towards evil? Is it more or less than the actual "evil" aligned recruits like brigands and theives?

You can find those in unit.var.

Anyway it's -1 for barbarian/shaman (unscrupulous), -2 for evil units, -3 for undead/demons.

Not too bad then. Bigger problem is their morale penalty once you are "The Pure".