Here is a game where I showed some of the power of Horse Traders in a Duchy/Duke Strategy. My opponent was Blooki (Triceratops), consistently a top-10 player on Isotropic. Here is the spread: cards in supply: Duke, Ghost Ship, Horn of Plenty, Horse Traders, King's Court, Moneylender, Royal Seal, Smithy, Walled Village, and Wishing Well
Note: I'm using the abbreviations HT for Horse Traders and WV for Walled Village.
Blooki went first and opened Silver/Moneylender. I opened Silver/Horse Traders.
Blooki WW
Turn 3: 4-> Walled Village 6->Duchy
4 Moneylender,6->Gold HT, 5->Duchy
5 Moneylender,6->Duchy HT, 5->Duchy
6 WV,4->HT (return WV) 4->HT
7 WV, Monelyender, 8->Duchy (return WV) 4->Silver
8 WV,3->Silver (return WV) HT,4->HT
9 WV, HT, 6->Duchy (return WV) 4->Silver
10 WV, 6->Duchy (return WV) HT, 5->Duchy
Okay, there are a few things I want to point out here. All the Duchies are now gone, I've just gotten my fourth to make it an even split. I could have bought a gold on turn 3, but with the HT strat, I think this was the right way to go. I'm not sure about blooki buying a Duchy rather than a province on turn 7 - yeah, he wants to deny my, but he's trying to win the game on provinces (I think), and he's really hurting his chances to do so. I think on one or two of the fours that I went silver, I should have gone HT. I probably also should have bought coppers with some of my extra buys. Moneylender doesn't seem to work well with Duke boards. But the thing that sticks out like a sore thumb is WV, which just looks worthless here. Also, you can assume that Walled village is getting returned every chance it can (I'm going to stop putting it)
Blooki WW
11 WV, Moneylender, 3->Silver 3->Silver
12 WV, HT, 5->Duke HT, 7->Duke+Estate
13 WV, 8->Province 5->Duke
14 WV, 3->Silver HT, 7->Duke+Estate
15 WV, 3->Silver 0->Copper
16 WV, Moneylender, 5->Duke HT, 6->Duke+Copper
17 WV, Moneylender, 8->Province HT, 6->Duke+Copper
18 WV, 3->Silver HT, 5->Duke+Copper
19 WV, 4->Smithy 3->Estate
20 WV, HT, 5->Ghost Ship HT, 5->Estate x 2
21 WV, 4->HT 3->Estate
22 WV, HT, 6->Gold 4->Estate
23 WV, Moneylender (no copper), 2->Estate
Game Over
Decks:
Blooki: 2 Prov, 2 Gold, 4 Duchy, 2 Duke, 1 GShip, 2 HT, 1 Moneylender, 1 Smithy, 1 WV, 6 Silver, 4 Estate, 1 Copper
WanderingWinder: 4 Duchy, 6 Duke, 3 HT, 4 Silver, 10 Estate, 11 Copper
Final Score: Blooki 36, WW 46
Obviously imperfect play from both sides here, but still fairly good, and I think this shows the general strength of the HT+Duke Strategy.