Priest needs cards that shuffle copies of cards into their deck. Maybe shuffle a/all card on the battlefield back into their deck and copies into the priests deck, or shuffle a random card in the opponents hand back into their deck, along with a copy into the priest deck. To give mysterious visitor some value.
Also, should have cards that have over heal to reduce the cost of copies. As the priests are usually over paying to play the cards when others are getting copies discounted.