I see your point about Cultist 2.0. Cultist 1.0 had problems too... How about instead of potentially crippling other people's engines, every cultist you've played forces other players to discard 1 treasure from their hands, or reveal their hands if they have no treasures left? That way, most action chains are immune, and it punishes Big Money. And Cultist provides money so it's a good counter to itself.
Dominion steers clear of attacks that, even in fringe cases, completely lock an opponent out of the game. The only case I can recall is a KC x2, masqueradex2, goons combo. In this case, if you can throne room or KC a cultist your opponent loses a turn, end of story, unless he also goes cultists or has some sort of conspirator/minion thing going for him. Also note that Cutpurse v. 1.0 had a similar attack and got very annoying very fast. From Donald X's notes on the seaside cards:
"Cutpurse: This started out as "Cards cost $1 less this turn, then $1 more until your next turn." That doesn't have the same timing as the other duration cards - it goes away at the end of the previous player's turn, rather than at the end of your turn. The developers didn't like that. I replaced it with "+$2, name a treasure card, each other player discards it." That was quite strong. You don't have to discard Gold very many times before you're sick of it. I reined it in by having it only hit Copper. It's still quite annoying if multiples get played against you early on."
That said, it may well take an attack that strong to convince someone to buy curses. At least it doesn't target a specific treasure like the Cutpurse beta did, and it's very difficult to buy early - $3 + (potion equivalent) is roughly a $5 buy.
As for Port Tax, how about I remove the VP penalty, and boost it to a +$5? And everyone gains "a curse or copper, your choice" when they make any buys beyond their first?
Penalizing +buy essentially punishes players who aren't going big money, and +buy cards like market and woodcutter are already rather weak. Note that $6 + (potion) has more opportunity cost than a *province* so this card is also wickedly expensive for a curse-giver that almost never curses.
For Census I actually thought of the flavor to fit the function. I had cards like Transmute in mind when I decided to make this one "all over the place". Revealing an action gives you an estate, which initially bloats your deck by a little, but if the Census reveals the estate you gained, it's a free, action-less VP token (plus, in the endgame, who can argue with a free victory card?). Revealing a treasure gives you a gold, which is worth more than the ~$5 this would have cost. All the while it helps you cycle through the deck a little. In the end game, it gets risky with Provinces, but can help you grab a win-defining Duchy if you keep a Curse or Taboo. In the earlier game, the self-trashing function is more like a $5 feast to grab $6's.
First off, Census's text doesn't actually fit on a dominion card. Second, a card that can trash multiple provinces into duchies is not going to get bought in the endgame, ever, and a card that gives you estates in early game for drawing actions isn't really worth it - your deck is *already* going to be bloated because you got curses, and estates make that effect even worse. Third, transmute is entirely unlike this card because it gives you a choice, and this one doesn't.
That said, I really like the idea of playing russian roulette with your own deck, but this card is way too expensive and comes way too late in the game to be worth it.