I haven't had the time to go through all the cards yet, but food for thought. From Donald X secret history of Dark Ages,
Hovel is the only one that changed. Originally it was an action you could trash by discarding your hand. It turned out that trashing it turn 1-2 usually seemed like the correct play, even if you drew it with four Coppers. So that was no good. Hovel as printed has nice flavor going for it; you move out of your old Hovel and into a nice Duchy.
So if you consider Wayferer as an empty card (it's a cantrip), it has the potential to degenerate openings kinda badly. However, when you consider that opening Doctor by $1 gives a similar effect, I'm not sure. On-buy Salvager is an interesting effect; I'm just not sure how balanceable it is.
Edit: So hey, I actually have time. So let's review cards now! Once again looking at every other card here. I've skimmed some analysis beforehand, but I haven't read all of it.
Palanquin
Types: Action
Cost: $5
+1 Action. You may discard an Action card. If you do, +1 Card per $ it costs.
I don't think it's as good as it looks, the restriction is a bit tougher than it looks. At the same time, I still think the effect is far too strong and impossible to balance to make it worth it.
Quagmire
Types: Victory
Cost: $3
Worth 1 VP.
When you gain this, trash 3 cards from a Supply pile.
I think this gives too much pile control. I mean, it doesn't sound too bad, until you get behind on a Wharf or Duchy split from luck and then suddenly that pile's empty.
Pilgrimage
Types: Action
Cost: $3
+1 Action. +2 Buys.
While this is in play, when you gain a Victory card, Victory cards cost $1 less this turn, but not less than $0.
Clarification: Buying this multiple times in a turn does reduce costs each time.
So, in theory, it's +$1 for each Victory card you buy. It looks scary, but 1 copy is okay. And then I realize wait this stacks, and now it's dangerously good. Still, neat idea.
Trade Agreement
Types: Action
Cost: $5
+3 Cards.
While this is in play, when you gain a Trade Agreement, gain a card costing up to $5.
Needs tweaking to avoid draining a pile immediately. Feels like a retread of Border Village to me, with an explicit cost. BV has a "less than" clause for a reason.
Emerald Vein
Types: Action – Victory
Cost: $5
+1 Action. Reveal your hand. +$1 per Victory card revealed.
Worth 1 VP.
I can just imagine having this in hand, and nothing else, and going oh come on I can't get +$1 off this to hit $8? Not inherently bad to act that way, but it hurts fun levels. Anyways, I can see it being very strong in engines and not really worth it otherwise.
Vendor
Types: Action
Cost: $1
+1 Action
When you buy this, +2 Buys.
No, I think trying to add a strong bonus to an on-buy with a useless top half is the "Blood Diamond" problem all over again.
Ring Leader
Types: Action – Attack
Cost: $3
+2 Cards.
When you buy or play this, each player (including you) reveals the top 4 card of his deck, discards one that you choose, and puts the rest back in an order he chooses.
The attack seems a bit too good, actually. 4 cards is a lot to look through. Think of Cartographer, and how often you want to keep a card in the 4 you reveal. Now imagine you don't get that. If the sample space was smaller, maybe.
Factory
Types: Action – Reaction
Cost: $4
+1 Action. You may discard a card that is not a Victory card. If you do, gain a copy of it.
When you gain a card, you may reveal this from your hand and put it onto your deck. If you do, put the gained card into your hand.
You can't Factory loop but you can sure gain a lot of copies, which actually start hurting you at some point. I like how it all comes together, it's a cool effect, but gaining with such low conditions is heuristically very worrisome.
Workers' Co-operative
Types: Action
Cost: $5
+1 Buy. +$3.
While this is in play, when you buy a card, each other player may gain a card costing less than it.
Oh it's the fixed card! Although I'm going to pretend it's a Contraband variant for variety. Like Contraband, you play it, and then buy two cheap cards instead of the big card you wanted. Fills a similar niche, not bad, I think similarly weak but not all cards can be Ambassador.
Witch Doctor
Types: Action
Cost: $4
+$1. Look through your deck; reveal and discard any number of Victory and Curse cards from it. Shuffle your deck.
When you gain this, put your deck into your discard pile.
I like the on play effect, the on-gain effect is a bit odd but I suppose it mechanically lets you get Witch Doctor earlier? It's not the best synergy; I play Witch Doctor, now I can't buy one or else I just shuffle all that stuff back in. Gains during turn would be interesting though.
Shoreline
Types: Victory
Cost: $6
Worth 4 VP.
When you gain this, +1 Buy.
It's kind of boring but it's subtly game-warping. Does that make it a good card? Well, it's interesting to me.
Travelling Salesman
Types: Action – Reaction
Cost: $5
Discard any number of Treasure cards from your hand. +2 Cards per card discarded.
When another player gains a Victory card, you may discard this. If you do, gain a card costing less than the gained Victory card.
Reaction seems too annoying, just conceptually. Even if limited to non-Victory, it's so strong.
Oicho-Kabu
Types: Action – Victory
Cost: $5
+1 Buy. +$2.
Worth 1 VP. While this is in play, when you buy a card, +$2 and discard the top card of your deck. If it's a Victory card, trash this.
I'm probably missing a reference. +$2 sounds strong, I suppose it's supposed to balanced out by the trash clause, but I'm not convinced it makes it any better. Pretty good in the building part of engines, very good actually if you pick it up around the middle.
Okay actually this is going to take a while, I'll start from Sultan later.