Mine (Action, $5)
+1 Coffers
You may trash a Treasure from your hand. Gain a Treasure costing at most $3 more than it into your hand
I think if you wanted to make Mine a decent $5 card, giving it +$1 would be sufficient. I bet +1 Coffers is even a bit overboard, power-wise. Plus it's introducing a new mechanic to the card, making it especially not at home in the base set. I know I added Horses to Transmute, but in order to keep the core concept of that card, it had to gain some specific Action, and gaining another Transmute is usually just awful. I might yet replace Horse with some other custom Action card.
All that being said, I like Mine fine as it is. I still buy it, what can I say.
Harem (Treasure/Victory, $6)
$2
+2 buys
-
2 VP
In games using this, when you gain a Gold, you may exchange it for a Harem
Well it's a neat idea, Gold replacement. I would not use it here though, because that's three kinds of timing, needing two dividing lines. Also I like Harem for $5 just fine. I like to maintain simplicity where I can.
Cursed Village (Action, $5)
+2 Actions
Draw until you have six cards in hand.
-
When you gain this, take "Cursed entry"
Cursed entry (state)
At the start of your turn, discard down to 3 cards in hand and return this.
OK well here you're just asking the wrong audience. Basically the only two groups the tested Nocturne were Donald X.'s group and my group. We really like Hexes. If we didn't, it's possible they wouldn't be in Nocturne at all. I don't want Cursed Village to be less random! That's half the fun.
Also I don't love how the penalty becomes an advantage once you start having Cursed Villages in your hands. Discard two cards, but then draw up to 6? Yes please.
Stash (Treasure, $5)
$2
If you have played at least 2 Actions this turn, you may put your deck into your discard pile.
-
When shuffling this, you may look through your remaining deck, and may put this anywhere in the shuffled cards.
That reminds me.
Again, I go simpler when possible. And I'm at the point in my Dominion-testing and fan-card-making career that I can say, I don't believe in the "no Silver+ for $4" rule anymore. My feeling is, if you're playing the kind of engine board that's likely to 3-pile, chances are you are not running out the Stashes. And on money-ish boards, I sure would rather buy Stash for $4 over another Silver. Spice my deck up a little, you know? Somehow Patron isn't ruining the games its in, and I doubt $4 Stash will either.
Anyway, sorry for being such a naysayer. A lot of this is just a difference in design philosophy between the two of us.