The Cleric represents something not present. A representative of an outside force - the Church hierarchy, or a God. The other classes could be agents in a similar way, but the Cleric alone must be. A mystic seeker seems better represented by the Magic User, unbound by the titles and ethos of a firm known structure. A Cleric cannot be a force unto themselves - unless they are a Heretic. The Heretic is against an orthodoxy. They are unsupported by their‘home’ religion - consider that the OD...
