So I got to try out Dark Thresh today.
List:
//Creature
3 Deathrite Shaman
4 Delver of Secrets
4 Nimble Mongoose
//Instant
2 Abrupt Decay
4 Brainstorm
1 Counterspell
4 Daze
1 Dismember
3 Fatal Push
4 Force of Will
2 Spell Snare
4 Stifle
//Land
4 Polluted Delta
4 Verdant Catacombs
3 Tropical Island
3 Underground Sea
4 Wasteland
//Sorcery
2 Painful Truths
4 Ponder
//Sideboard
SB: 2 Winter Orb
SB: 1 Deathrite Shaman
SB: 3 True-Name Nemesis
SB: 2 Dread of Night
SB: 1 Abrupt Decay
SB: 1 Dismember
SB: 1 Spell Pierce
SB: 1 Surgical Extraction
SB: 3 Duress
I got weird matchups, so take everything with a grain of salt.
-Deathrite vs. Goyf is not a huge difference, especially with Fatal Push in the format.
-Mongoose is better than Goyf for sure.
-The deck's creature base is really flexible and smooth, which is cool. You can reasonably go down to seven creatures against removal heavy decks. Boarding out Mongooses entirely is totally fine as well, leaving you with 11 evasive threats.
-I don't think I've killed a single creature with Push that would not have died to Bolt.
-I did not get to play against combo, but having discard against Miracles is cool.
-Not having Pyroblast stinks. I don't think Decays do enough to remedy this. I would not mind an extra piece of countermagic, maybe a second Counterspell.
-Dread of Night is sweet, but I'm not sure how good it is vs. Mentor yet.
-I kinda want to draw Orb more often.
-Painful Truths is still amazing. I got to draw three turn two on the play with Daze & Force backup once, that was sick.
-I don't think I'm opposed to another land or maybe Life from the Loam. I considered my typical Loam + Ghost Quarter package, but I dismissed it to include both discard and Dread of Night.
-The removal split seems correct given the colour limitations.
Overall, I often felt I was playing a worse version of Canadian, but there is merit to playing this list. I think this deck beats at least the other three-colour Delver decks, and it's probably the best version against UR as well.