Per mtgtop8, Mire is actually the most used land in modern right now (Tarn is second). If their supply was equal Mire would quite likely be above Tarn in price tag.
You also have to recognize that tarn is also widely played in legacy and is the most played fetch in Vintage. While wide-scale reprints would likely bring Tarn's price down, I still would guess that it'd still be more pricey than Bloodstained Mire.
I don't have the numbers, but I can't imagine that the number of people playing paper Legacy comes close to the number of people playing paper Modern. Sure, Tarn is big in older formats, but if Modern has 10x more players (not sure of actual numbers, but wouldn't be surprised) then Legacy's impact on the price is so much less, let alone Vintage, a format that almost solely exists on MTGO.
Because Surveil is generally more powerful, I don't think it will phase Scry out. Scry is a really neat quarter-mana-cost effect to toss onto cards to sweeten the pot. Surveil plays into the graveyard, which means any future block with grave support would need to be more wary of using it, and if it had replaced Scry, that could make costing cards difficult in development.
Those are comments concerning ban-list items. I think others are saying that, when it comes to designing new and interesting cards for Modern, they've been pretty in-tune with the format. Arclight Phoenix spawned an entire archetype. Hollow One, same thing. Spectacle has a few interesting cards that are being toyed with. Azcanta is clearly a strong card, and don't even start on how Teferi powered up control decks.
They've been actively creating things for Modern for years now, with a pretty good record. To tunnel-vision on the banlist is disingenuous. Yes, it is a defining aspect of our format, but there is a much greater amount of change that comes from each new set they release.
My guess is a supplemental set that's Modern legal, because we know there are cards they want to inject into Modern but don't want in Standard, like Counterspell. [...].
Are there any sources for this? Are WotC actually looking for ways to bypass standard because they would like to make certain cards Modern legal?
MaRo has said they've discussed the idea internally. I think he's also said that he feels actual-factual Counterspell is about the right power-level for Modern, but would never get OK'd for a Standard legal set, at least not at the current accepted power-level.
I do wonder if they could have instead errata'd KCI to say that the ability can only be used any time you could cast a sorcery. That would have killed the weird interaction that allows sac'ing two things which see each other's sacrifice and would allow responses to a sacrifice to be more effective.
I think that would have made KCI weaker enough.
Making functional errata as a means to Nerf cards should never be used in Magic. It's a core difference between it and Hearthstone that the cards you open do what they say they do, outside of rules-clarification updates. To make it so that the only people who can play a card are the ones that have read up on the most current version of that card's rules is insane, and I hope Magic never gets to that point.
Deck was all kinds of broken; winning on multiple weird and non-traditional axes that are difficult to interact with, too quickly, and through several layers of hate. There are very few redeeming features and had multiple really gross showings on camera at multiple large paper events at the end of the year. It's ban came as a surprise to nobody.