The effectiveness depends on how good you are at casting them versus the level of your opponent ... whether they are even affected and how long the effect lasts.These are all helpful in defeating the breeders, as is throwing an elemental (or two) in between you and them. Guardian angel helps, as does having all of your "buffs" in place.
The shaman is back down at the pagoda, but you can't see him without the right ingredients ... ask fuzzfas about the seventh bough.
Tools for Wizardry(r) 7