Two questions:
One - Do good shamans traditionally use demonfire?
Two - If I wear a -wis item will my supplications suffer for it, if it reduces my overall wisdom?

1. Yes.
2. Most don't care, although some will.

nt

If it is on your skill/supp list do not be afraid to use it. Good characters can't use evil skills and vice versa, it shows up a lot more with the healer class. There's nothing wrong with using demonfire on a good shaman.

As for the -wis absolutely yes, you never want to lose wis as a communer class like paladin/shaman/healer. The lower your wis goes the less effective your communes are and the more you lose your concentration when trying to use them! It is why cranial is so tough against communer classes.

A a good shaman I wouldn't use demon fire. The very nature of the supplication suggests it's not a goodly thing. I suppose you could justify its use with your role but you'd have trouble for sure depending on which faith.