Here are my thoughts on Cartographer / Wishing Well. Any feedback would be welcome. I'm not really the best of players, I just played a good (3-player) game with it.
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When Intrigue came out, there was Scout / Wishing Well, but this turns out to be not so powerful. Sure, the Wishing Well turns into a Lab after playing a Scout, but Scout itself is weak outside of certain special cases. Its cycling ability is limited to green cards; if your deck contains few green cards, Scout usually replaces itself at best.
Enter Cartographer. It has two major advantages over Scout. One, it draws a card, so your handsize never decreases. Two, it allows you to discard any of your top 4 cards, not just the green cards. If you end up discarding green cards to Cartographer, then it gave you exactly what Scout gives, plus an additional card.
But what makes Cartographer even better when paired with WW is the ability to chain the combo in a way that Scout can't: you can use this combo to draw more of itself. The sifting ability of Cartographer paired up with the +2 Cards from WW all but ensures a decent hand every turn. It also becomes easier to play that powerful terminal action (Goons, Ghost Ship, Trading Post, etc.) lying somewhere in your deck. Both Cartographer and Lab are worthy $5 cards, but since WW costs $3 it is faster to set up this combo than to buy both Cartographers and Labs. The low cost of WW allows it to be easily bought with +Buy, gained with Workshop or Ironworks, or remodeled from Estates.
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That's all I have so far, any thoughts? I played a few solo games and it really depends on the board. With strong trashers like Chapel, there are usually better strategies. With Trading Post, I get 4 Provinces in 15-16 turns. It might work "better" with attacks, or it might just an illusion since Cartographer can weaken enemy attacks.