Stephen, there is an important concept when interpreting numbers: Correlation is not causation. What this phrase requires is that you add the context and assumptions to all numbers when attempting to infer things from them.
Top 8 numbers on sideboard cards are highly irrelevant because they are very often not the reason the deck is performing well. This is a classic correlated by not caused reasoning.
That principle - a generally acknowledged statistical and scientific principle - has no relevance here.
If you are saying that Top 8 appearances is just correlation, and doesn't reveal anything about a format, I disagree.
If there are literally dozens of top 8 appearances for a particular card, it suggests quite a bit.
First and foremost, if a card is appearing in sideboards, but not maindecks, then that is an important signal in and of itself. It means that the card is quite important at certain matchups, but the structure of the metagame is such that that card isn't good enough against most matchups.
Thus, take 2008: If Leylines are in 90% of sideboards, but 0% of maindecks, then that signals that a the card is tremendously important (and the reason it was important was primarily Flash, and secondarily Dredge), but it's not of broad enough utility to employ maindeck.
Top 8 appearances of particular cards are a signal about the structure of the overall metagame. Evaluators and format analysts must then use judgment to assess what that information means. But to say that it is 'irrelevant,' as I said, is dumb.
Especially when we look at Dredge hate, where nearly every deck has 4-10 hate pieces. You are guaranteed to find something like 32+ Dredge hate cards in every random top 8.
On top of that, we have the top 8 cut point bias. You needed approximately 3 wins to reach a top 8 at NE events for a long time.
Our Top 8 methodology excludes tournaments of 32 or fewer players, so the cut-off point is usually 4 wins. And, in any case, the vast, vast majority of data points in our data set are Vintage Challenges, which are mostly 7 rounds now.
To bring this back to this card, this card could get some top 8s. That won’t suddenly make this card better or more impactful. We can read it and realize it does not hurt near 50% of the metagame. People can put it in their Flusterstorm/MB trap/Pyroblast slots, but let’s not pretend that these other cards you are playing it over aren’t also very powerful.
It's not about "power" in the abstract. It's about how a card interfaces strategies in the metagame. The existence of a card - maindeck or sideboard - over time signals a structure. Lots of Pyroblasts signals strategically significant blue spells.
Similarly, lots of Stony Silences or Hurkyl's Recalls in winning decklists signal something about the metagame. You can extrapolate that further.
It doesn't matter whether a card appears in a maindeck or sideboard - when you see patterns in deck construction, those are signals about what's happening the metagame, not "irrellevant" information or noise. It's a signal about the structure and leverage points in the complex system that is the Vintage metagame.
I think this card will see more play than Damping Sphere because:
it is great against big blue decks, and basically a silver bullet against PO
it is frustrating for cantrip-based Xerox decks
It slots easily into Survival and WhiteEldrazi, two upper tier strategies and can be used easily by lots of marginal strategies, like Landstill, emergent combo decks, etc.
it's hyper-efficient, and a reliable first turn play
it can just steal wins in a Mox format, the same way that Chalice used to. Even against matchups where it's supposedly "bad," it can steal wins, like when Shops keeps Mox, Mox, Sol Ring, Factory.
Damping Sphere only had 10 top 8 appearances. I think this will have more, but also be a Vintage playable for a long time.