Why not make it to where any PC can pray at the shrine (like random people do at a temple) but it takes double the time to pray in comparison to a priest with an artifact per PC? 

So without a priest you have 0.5 PP per turn at the shrine, with the priest away from the shrine it's 1 PP and with the priest and the shrine it's 2 PP

OR in other words, Norm player takes double the time to pray when at the shrine (can't pray anywhere else though), a Priest player can pray anywhere at normal prayer amount and when the priest is at the shrine it takes half time to pray. ?? O_o

Just an idea to help. I see that item thing being abused greatly.