[Baalz]

Yes, the primary problem with communicants is that of opportunity cost. As you point out, you could have theurgs instead, and you've got a limited number of castles. I will say though that in testing this last night I did do a very nasty linebacker communion with communicants - 8 slaves, 3 masters. Masters cast mistform, personal luck, twist fate, quicken self, mirror image, breath of winter, then the masters fired the bows I had equipped to them. Pretty hideous damage output and the mistform + luck + twist fate made the communicants last plenty long enough wielding that quickened frostbrand to deadly effect....