I don't like these Ruinses that much from what I can tell. Just like with Black Market, it's swing-y. Assuming four of the five are +$1, +1 buy, +1 card, and +1 action, some are easily better than others. The fifth might be a lucky +1 VP, who knows. But, if I'm building an engine deck, I'm much happier with the +1 buy than the +1 action. And that I can get one but my opponent, who is mirroring me, gets another, is very frustrating. It introduces more of what I don't like in this game (lack of equal opportunity gaining), joining Tournament and Black Market in that regard.
In terms of power, I'd say that Cultist is about equal to Witch. The chaining and card draw is very nice, but I doubt there will be much chaining before the Ruin pile is gone. The trashing is nice. The Ruins still clog up the deck like the Curses, but the VP difference is non-negligible. I'd put it at moderately worse than Witch given the currently available cards, though if DA has more trashing, it will probably be equal to Witch.
I bet Ruined Market will be one of the better, if not the best, Ruinses.
Feodum seems to make games boring, with lots of money. It likes Trader, Trusty Steed, and boring decks, obviously. I think it will be very good in BM games. Buy 'em early, and then trash them as necessary and buy Silver without remorse if you are too clogged. It's not really rush-worthy because having means of trashing is paramount, and it's not necessary. If you can get five of the eight, and trash two, you'll have late game tempo advantage (from lack of two VP's and six more Silver) and the more valuable Feodums. I'd say it's almost a must-buy in BM games that feature some sort of trashing (Masquerade, Salvager, Apprentice, etc.).