I'm not sure why "HD 5+ creatures joining a new church" makes any sense. If you mean Magic Circle Against [Alignment] a) it's also on the Wizard/Sorcerer list, b) not every HD 5+ creature is going to be with a spellcaster capable of casting it 24/7, c) alignment and religion actually don't matter at all for the compulsion suppression effect, and d) ...seriously? Your argument against "mind-affecting abilities are strong" is "lol then every creature at CR 5 or higher joins a church and has a cleric glued to their stomach"? Please tell me it's not actually that.