Should the Balor's magic resistance protect against Ghoul's Touch? I have found that I can kill it pretty easily with that spell. It routinely fails the magic resistance, gets held and a fighter then uses coup de gras.
Balor's magic resistance, assuming it is 30, does not grant him immunity to spells, especially if your caster has the magic penetration feats. Though normally the spell: Ghoul's Touch should NOT work on him, as he is an 'Evil Outsider' type creature and not a 'Humanoid'. I never used it on him, as I always expected that it will work only on humans, goblins, etc. It must be an oversight by the original developers. Did you use successfully Ghoul's Touch to other creatures, like animals or elementals?