Thanks for sharing, interesting reading.
But I have to say I disagree with one of your statement:
"So yes, in Turbo Depths [Once Upon a Time] is not bad, but also not better than the existing cards (it does provide a free replacement for a faster combo)"
And here is why: Turbo Depths is a deck that plays 0 to 4 Sylvan Scrying (a lot of the Slow Depths list have cut the card completely), depending on the version played. Well, I think Once Upon A Time is actually doing a much better job than Sylvan Scrying. And you have to compare it to this precise card, because both cards are used almost in the same way and are in direct competition. Unlike Crop Rotation , which is (at least in Depths decks) clearly superior and a must-have card. Same idea with Elvish Reclaimer: it is not only an instant speed tutor that use no land drop (same than Crop Rotation) but also a creature with a good body. You could also maybe compare it with Sylvan Library, but I think that would be a mistake, since Sylvan Library's purpose is clearly different.
So, to sum it up: I think that in Turbo Depths, the only card that we should compare to Once Upon A Time is Sylvan Scrying. And if we compare both cards, Once Upon A Time is in my opinion strictly better than the only existing card we can compare it to:
Once Upon A Time compared to Sylvan Scrying
con:
- search only in the top 5 cards of your library.
pro:
- can also find creature cards.
- is an instant.
- can be played for free if it's the first spell you play.
So...this is pretty clear to me: pro > con !
Of course, this is only my opinion, based on my intuition and supported by the testings I did until now. So please tell me if you disagree, and why (maybe your testing went differently than mine!)!
I might have missed something, but only the fact that a famous Depths player like DNSolver still choose to play Sylvan Scrying over Once Upon A Time makes me question again this whole comparison. And truth is that until I get a new explanation or new data from testing, I think it is sub-optimal to run Sylvan Scrying over Once Upon A Time.
And also: "So yes, in Turbo Depths [Once Upon a Time] is not bad, but also not better than the existing cards (it does provide a free replacement for a faster combo)" --> I want a faster combo every day!