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Hybrid decks are pretty common in vintage - I think I've seen just about every two "pure archetypes" smashed together. Ever see someone play turn 1 Workshop->Trinisphere, turn 2 Orchard->Oath?
I don't think it's possible to say "Hybrids are good" or "Hybrids are bad", there are tradeoffs with everything ... but it's definitely something people have done and had with success with. If that's what gets you excited when you're building decks, I'd absolutely go for it.
@Brass-Man thank you for the reply, i wasnt sure if there was a definite answer to if they are bad or not.
I like deck hybrids, but really the "best" hybrids aren't hybrids that fit 2 gameplans into the same 60 cards....those tend to get the wrong pieces to the puzzle you are trying to solve at inopportune times. Workshop, mox, oath is a nonbo...so is mox, orchard, trinisphere.
*This is not to be mistaken with a "plan B" that typically takes only a few slots and is synergistic with your plan A (think tinker/colossus in a tezzeret/vault/key deck).
The "best" hybrids, in my experience, are ones that try to utilize the whole 75, and the sb plan is basically a transformational deck that dodges the sb hate, has some synergy with your original plan, but isn't beat by the same hate cards. Think dredge/Divining witch/maniac....or dredge/dark times. I have had some success with things like workshop/dark times hybrids, but that is more because the cards are all complementary to each other's plan (they don't hinder each other or in many ways help each other). These type of hybrids tend to be great when they work well together, but still give you awkward hands. They require mulling more aggressively and good draw/filter/luck.
If your sb swaps out one plan for a new one (dragon/tezzeret did this well, and hermit druid/oath is my all-time fav) it is more likely to be a strong, linear design your opponent isn't prepared to stop (even after sb).
Wasn't there an interesting Oath + Doomsday hybrid roaming around?
I was working on Workshop Oath for a while. You either oathed up Lodestone Golems or hit Sundering Titan. That idea is kind of in the trash now.