IMO, the best religion would be one that has many noble followers and no temple. The priest game is a distraction, it makes you focus on follower counts and infrastructure maintenance instead of on influencing other characters.
I wouldn't go so far. However, I agree with your basic point: the interest of the religious game is in influencing other nobles. All the game-mechanics options for priests are technically influencing peasants; however do not think you can get away with any of them without at least some powerful nobles backing you out.
The point of a religion is to create a culture among a noble group. Once that culture is in place, the Lords will build temples for vanity. I doubt doing it the other way around can be fun.
