Cathedral: Based on how broken Lurker+Hunting Grounds is I'd be careful with Cathedral, I don't think it's too strong but it seems pretty one dimensional. Like you rush Duchies with it and that's about it, I think a Crossroads/Shepherd like thing would be more interesting to someone who likes to green early? Something to incentivise early green rather than just Duchy gaining.
This is a really good idea. I think I'll head in this direction. It feels like gaining Duchys is just too situationally beneficial or not.
Possibly this idea:
Cathedral Cost:6
Action
Draw 3 cards
Put this card on your tavern mat.
During your buy phase you may reveal a hand with three or more victory cards.
If you do return Cathedral to play and +$3
This could be a little weak at 6 but at 5 cost it feels way too strong. Its potentially +3 cards and +$3 in the same turn. Particularly in games with tunnel or nobles.
I'm not so sure Arcane Chest is so bad as people feel though. I'd rate it about as highly as contraband except unlike contraband you might actually want to play multiples of this. It wouldn't be the first 5 card I bought but it might be in there.
I am coming round to the view that the drawback (the benefit to others) on Blessing is too high. I still want to combine some card draw with trashing and that is significantly strong. I'll keep tweaking that one I guess.
I appreciate all the comments. Thanks.