4 is perhaps my favourite cost to design for, so at least to a certain extent, this is the heart of the set. Anyway, here are the first few:
I hesitate to say something that might be construed as "your perspective is wrong", but I'm gonna interject a note on viewing costs in general.
In my mind, there are 2 categories of cards in Dominion: weak cards and strong cards. (Maybe there is also "junk", a third level below weak.) Weak cards cost 2, 3, or 4; strong cards cost 5, 6, or 7. There is almost no difference between 2/3/4, nor 5/6/7. There is a canyon between the two categories--the grand canyon, filled with lava.
Costing a card at 5, 6, or 7 is mostly just a matter of "How early do we want people to be able to purchase this?" so that's easy. Costing a card at 2, 3, or 4 is a function of how beneficial the card is when spammed, whether or not we want to permit it as a double opening, and if we want to allow purchase as part of a 5/2.
Chapel and Lighthouse are really powerful weak cards but they cost $2 because there is no reason for them not to. Then you've got stuff like Treasure Map which has to cost 4 because allowing a double-TM opening defeats the point no matter how you balanced the reward. Then you've got say Lab which is a really powerful strong card, but it's okay at $5 because getting it early isn't a concern. Meanwhile on most boards Forge isn't that amazing compared to other strong cards, but it has to be $7 because it can't be freely allowed into the game that fast.
I'm probably preaching to the choir here, since the pope has said all of this before. The point of this long-winded preface is that I won't be looking at these as "the heart of the set", or meat-and-potatoes. I'm going to be looking at these as just weak cards that for some reason can't be $3. (or $2)
Depository
Victory 4
Worth 1 VP for every 5 treasures in your deck (round down)
So 10 seconds ago I thought this was a fantastic idea, 5 seconds ago I thought it was actually a bit lame, and now I hate it. This is an alarming subjective trend.
Here's the problem: This is very similar to Gardens/Vinevards, except that Gardens/Vineyards is fun. Gardens/Vineyards has the impact it does because making a cool and fun Gardens/Vineyards deck is how you feed it. Your buying engine Woodcutters and Workshops, your game-ending Estates and Great Halls, your token 3rd-pile Havens and Pawns, all that fun stuff counts. These factors and their flexibility are what ultimately makes these alternate victory cards soooo cool.
But then here well, all there is to it is "maybe get +buys for coppers" and "be biased in favor of Big Money." Yawn. At the end of the day... Actions are fun, Treasures are lame.
Regent
Action 4
+$2
Name a card. Reveal cards from the top of your deck until you reveal the named card. Put that card back on top and discard the rest.
Donald X pointed out that this is strictly superior to Chancellor, and that really,
really bothers some players.
Good news is, I'm not that guy. Bad news is, as a designer, I share Donald's terror of that guy. I suspect he knows where I sleep, and you too. You can see it in his OCD eyes. In fact I'm 99% sure that if you attempt to push this card, he will try to sneak into your house at night and delete it from your hard drive.
The Strictly Superior Suburban Slasher is not a joke, and should be taken seriously.
Medical Tent
Action 4
+2 Cards
Discard any number of cards
+1 action for every card discarded this way
Seems pretty good. It's presumptive of me to say this without playtesting, but this is probably a good example of a well cost card. It's powerful, but not nearly powerful enough to cost $5+. However, since that power comes from it being a spammable engine enabler, we can't have it costing $3.
I always worry about cards that give lots of actions (beyond a basic +2 village), since the value of mass actions is so wildly variable. But it's not a concern worthy of shooting down cards for.
Swing
Action 4
+4 Cards
Discard 2 Cards
First I thought this was too powerful, then too weak, and now I've just concluded that I'm too stupid to properly guess.
I think I like it though, for sure. It's very dynamic since it has implications with a lot of cards. It's definitely better than Smithy for combos. It's like, this:Smithy::Smithy:Envoy. And that's neat! It burns through your deck faster but gives you less card advantage. Definitely cost correctly at $4.
Looter
Action-Reaction 4
+1 Card
+1 Buy
+$1
You may discard a card. If you do, +1 Action
___________________________________________
Whenever you discard a card, you may set this aside from your hand. If you do, +1 card and return this to your hand at the beginning of your next turn.
I'm so confused about the name. Looter should be an attack, right? I mean, it's a bad guy who takes stuff.
I'll be honest, I don't understand anything about this card mechanically either. So it's like a Market, but you have to discard to get the Action. Why? Oh, but it has a reaction on discard. Why? It gives you this self-perpetuating +1 Card. Why?
Come to think of it, this card is absurdly powerful. With discard procing cards in your deck, this is almost better than Alchemist. So it's either a super engine that can't be stopped once it hits critical mass, or it's a mediocre and random $4 grab bag of stuff. You've got some explaining to do before I bite on this one.
Expedition
Action 4
+1 Card
+1 Action
Gain a silver
Hmm, I think I like this. It's narrow and varies a lot in utility (on a lot of boards it would never get touched), but elegant.
Does it have to cost $4 though? It's spammable, but how powerful is it really? Buying this twice as an opening is not promising at all for your turn 3/4 buys...
Exhaust
Action-Attack 4
+1 Card
+1 Action
Every other player gains a copper
Truth be told, I don't think this is probably too powerful, at least on most boards. You guys probably think it is, and I have some nerfs ready when you're proven right.
Yeah, we need to talk.
So first off, cards that give people junk are *really* powerful. A Copper is not nearly as bad as a Curse (or Estate), but it's still *really* bad!
Second, spammable attacks are both obnoxious and really powerful. Comparable Spy attack strength to terminal attacks--it's not in the same ballpark, or even the same sport. Makes sense, since palying 5 Spies is easy and playing 5 Witches is, thankfully, super hard.
Familiar is the exception that proves the rule. The only way a strong, cantrip attack can exist in any sane way is with a high cost involving potions. Getting Familiars requires two entire deck cycles, and that's just for one! Your ability to actually get Familiars to spam as you'd like is super constrained by the economics of Potions.
And here you are proposing a cantrip junker you can get as an opening--
any opening! Sorry chief: Three minutes in the penalty box for this one.
Agriculture
Action 4
While agriculture is in play, victory cards gain the treasure type (in addition to their other type(s)) and can be played as treasures for $2
Okay, this is awesome. I'm trying to think of a good reason why this sucks and shouldn't exist, and I really hope I fail. Hmm, gimme a moment, this might take awhile.
Okay, I found something, but it's an easy fix. This let's Thief/Pirate Ship trash enemy Victory cards! Make it only work on yours and we are golden.
This is crazy good with Scout, Great Hall, Nobles, and Harem. But that's all okay. Mint and Mine really push it, but we can give it a pass.
I haven't really considered the power level yet. This might work better as a non-terminal $5+ card? Just thinking out loud, I have no idea.
Edit--As fun as type modification interactions are, we can remove all the fringe cases by just dropping it: "While Agriculture is in play, Victory cards in play produce +2 money; during the Buy phase, you may put Victory cards from your hand into play."
Moneybreeder
Action 4
Discard a silver. If you do, choose one: gain a duchy or gain a gold.
I feel like this is sort of an uninteresting alternate economic path. It's just seems like a really boring way to use your Action and $2? It's also a surprisingly poor opening, I'm almost certain.