I do pick it up. I sort of always thought 18 gold was too much for the effect, but anything that messes with piety gain is quite strong due to being flexible. I think it was ment to help with pactmaker mainly. If I overthink it a little, maybe the problem is that in the scenarios where you can easily harvest piety with it (sub vicious dungeons) you don't really need it, and in the scenarious where you want to play tight - you can't really go killing monsters left and right.
It is, IMO far overshadowed by the crumbling ward. That's an identical looking subdungeon item (found in the south) which you can locker. It converts (or can be used for) gaining +15 piety on the spot. Maybe swap those two around, make the crumbling ward effect what you unlock with priests, and the other one what you find in a subdungeon?