I had no trouble against alchemy using these decks:
- Eithne Shupe (Aglais is MVP, Brouver/Hattori also provides a lot of tempo, artifact compression worth a lot of points and removes targets for ointments, Shupe mage can win you the game single-handedly by casting weather, drawing a card or stealing a buffed unit)
- Foltest Knight-Elects (knights were killed by the witchers, but my witchhunters reset his buffed units, and Dijkstra provided tempo)
- Veterans with Birna (because 90% of alchemy decks didn't have weather clears)
- Harald Axemen (it was always fun to watch alchemy players passing with +2 CA to get destroyed in a long round).
- Tempo-reveal Calveit with Letho and Regis (since alchemy has high str units)
- Swim's big monsters with Imlerith: Sabbath (Imlerith was usually killed, but ghouls, Toad and Ozzrel provided a lot of tempo)
I am talking about high level ranks, 3900+ MMR
I didn't play autopilot decks like greatswords and consume, but I imagine consume also didn't have much trouble unless NG was very lucky (has mandrake in hand, shuffles it back with Assire, replays with Vesemir). And alchemy-GS match ups were determined by how many witchers NG draws to kill greatswords and ships.
Come to think of it, I listed 8 competitive decks that can be used to get at least rank 20. How many good decks are there in HC, eh?