In his article about the Aetherworks Marvel ban, Aaron Forsythe said that they had data to demonstrate that Marvel wasn't actually that good, but that it was unfun to play with and against. People got very frustrated when their opponents had a turn-4 or -5 Ulamog, and for good reason—those cards weren't meant to be cast on turns 4 and 5. He also said on Twitter that, ultimately, it didn't matter if WotC was right or not (regarding the deck not being too good) if people just didn't want to play, and people didn't want to play because Marvel was the most popular deck in Standard. Basically, it's OK to have a perceived best deck, but it's not OK to have a perceived best deck that people hate so much. Death's Shadow is the perceived best deck in Modern, but they didn't ban that because people don't hate playing against it.
This reasoning makes a ton of sense. The goal of Standard is not only to be balanced, but also to be fun—people have to want to play Standard. People didn't want to play Standard, and WotC identified Marvel as the main culprit, so they banned it. This isn't about Twitter's public outcry so much as it's about Standard tournament attendance being down across the board, enthusiasm being low, and interest in Standard content dwindling more and more.
Part of the reason the card is so unfun is that the randomness of it makes Hearthstone cards look like paragons of consistency—for 4 mana and 6 energy, sometimes you get Ulamog, and sometimes you get… Attune with Aether. This type of extremely random, flashy effect (e.g., Ragnaros) works in Hearthstone, but the truth is that Hearthstone can afford this type of effect because they don't have mana issues—most of the game is remarkably consistent, so this is where you get your randomness. In Magic, there's a lot of inherent inconsistency already because of the mana system, so when you have a card as random as Marvel on top of that, I think it causes a problem. I don't mind variance and swings, but the swing here is just too extreme, and it will happen every single game the card is involved.
By being so efficient, Marvel also limited design space and diminished the excitement for future things. I remember when the new Nicol Bolas was spoiled, people's comments weren't, "wow, Nicol Bolas is a ton of fun"—they were, "oh good, now my opponent can Marvel into that on turn 4 as well." Aetherworks Marvel is the kind of card that, simply by existing, means you cannot print certain other cards, and that's really bad.
One thing that I believe is a little misleading in Aaron Forsythe's announcement is the win percentages. Aaron states that most decks had a winning record against Marvel, but the numbers don't tell the whole story here because all of those decks are super tuned to beat Marvel, and everything that did not have a winning record versus Marvel didn't survive. Once you select only the decks that can beat Marvel as viable, then of course you're going to arrive in a metagame where things can actually beat Marvel. Do you know what B/G Delirium Control's record is against Marvel? Me neither, because no one plays it because it cannot beat Marvel. But, despite that, I think their arguments make sense.
"But PV, what about my Ulamogs?" Yeah, I hear you. I agree, it sucks. I bought 4 Ulamogs myself for last PT, for about $20 each. I played them once, and now they're basically worthless. The same happened with Saheelis, Emrakuls and Smuggler's Copters (which I actually bought and played with 0 times). I'm lucky that I get to bill those as "work expenses" in my mind, so I don't feel so bad, but I understand that for a lot of people this is not the case, and that's bad. I could easily be a high school student who finally got a deck together and is suddenly down a hundred dollars.
This is the main reason banning cards is bad, and why they try to avoid doing it at all costs. After all, there are only so many times I can have my deck banned before I give up and start playing a different format, or, God forbid, a different game. WotC knows this—they know banning cards is bad for them. The fact that they banned Marvel doesn't mean they're oblivious to the harm it's causing—it just means that they think it causes even more harm unbanned.
This is a really tough spot for them. If they ban the card, people suffer. If they don't ban the card, then people also suffer because the format is bad. Ultimately they decided that the lesser of two evils was banning the card. I think I agree with them, though I do not have all the information that they do.
The best solution, of course, is to never print cards like that to begin with. This is the goal of the new Play Design department, to make sure that mistakes like this don't happen again and nothing ever has to be banned. But, at this point, the card is already out there, so this is not a choice and they have to work with what they have.
When the Saheeli/Guardian combo was banned, Standard didn't actually change that much because the Marvel deck took its place as "oppressive combo deck that beats every durdly deck." With Marvel also banned, then I don't think there's a deck to take that mantle, so Standard will invariably change. Here are the cards and decks I think are going to be winners and losers with the ban:
Zombies is a powerful deck, with a good Mardu matchup, that got largely thrown out of the metagame because of its poor matchup against Marvel, especially as Marvel decks adapted to play Chandra, Flamecaller, main deck Kozilek's Return, Radiant Flames, Sweltering Suns, and whatnot. With Marvel gone, I think Zombies can truly shine.
Of course, other decks will adapt—Mardu decks might sideboard more Radiant Flames or Sweltering Suns themselves (or even have Chandra, Flamecaller instead of Sorin, for example)—but Zombies should, overall, be better than it was before.
Ishkanah is a very powerful card, but it's really bad against both Felidar Guardian and Aetherworks Marvel—you simply cannot tap out on turn 5 for a card like that and expect to win the game against those archetypes.
If you're playing against a fair deck that wants to kill you attacking with, say, Heart of Kiran, then Ishkanah is pretty good. All you have to do is make sure you're bridging into something. Because, you see, Ishkanah is very good at stalling the game out, but it's not that great at actually winning the game by itself, and Gideon will kill you at some point. This role used to be filled by Emrakul, but now that that's also banned, then those slow decks have to find another powerful win condition.
For G/B Delirium decks, this can probably be a combination of Noxious Gearhulk and Liliana, Death's Majesty, but it would be good to have something big. I rather like the white splash for Angel of Sanctions, for example. Or you can go with something close to Brennan DeCandio's list:
Another option is to have the ability to turn into an offensive deck at a moment's notice. The Temur Emerge deck that we also tested for the last PT has the ability to do this. It's a deck that I think is quite powerful but had many issues with Marvel.
Originally we had 1 Negate, but I think you don't want it without Marvel in the meta. I think Manglehorn is still good, as it's great against Vehicles and randomly kills Gearhulk and Mimic, on top of being a good Emerge outlet, but it's possible the deck should only play 1.
Regardless of how you build it, this deck is very good versus both Mardu and Zombies, and quite bad versus Marvel and control. In a metagame where Marvel is gone, it could be a really good choice.
New Perspectives isn't a great deck, but it can be very good if well positioned. Without Marvel in the meta, it's likely that people shy away from the cards that beat you—Transgress, Lost Legacy, and a plethora of Counterspells. If people take a Marvel ban to mean, "I can finally play those fair strategies that scoop to a combo," then this is the prime time for a deck like New Perspectives to take over.
Masashi Oiso and some other people from his team played the deck at PT Amonkhet. Unfortunately, they all did badly so I can't find a deck list anywhere, but this is the list we had:
Well, duh. It turns out 10-drops aren't that great when you actually have to pay 10 for them.
Lately, we've seen a big emergence of Spell Queller, be it in U/W Flash builds, Jeskai Vehicles, or 4-color Vehicles. This list that Ryoichi Tamada used to win GP Manila, for example:
Ryoichi Tamada, 1st place at GP Manila
This deck is good versus Marvel, but is probably not very competitive now that it's not in the format anymore, as it's just fundamentally underpowered. I expect this deck (and the blue splash for Spell Queller in decks like Vehicles) to basically disappear.
The White Splash in Zombies
The most interesting thing you got from white as a Zombies player was the ability to answer both Ulamog and Marvel itself with Anguish Unmaking. Now that Marvel is banned, I think the white splash is a bit unjustified. Gideon is still a great card, but I think the deck functions better as mono-black and I expect that to be the dominating version moving forward.
This is probably where this article goes the most against conventional wisdom. Most people seem to think that, with the Marvel ban, Mardu is going to dominate again. I don't think it will, because a lot of the cards that were good against Mardu were not played because of Marvel.
The biggest example of this is Zombies. Zombies has quite a good matchup versus Mardu (it's very good preboard and competitive post board), and I expect Zombies to increase in popularity because of the Marvel ban. Ishkanah is another card that is traditionally good versus Mardu that was kept down by the Marvel decks as well (I think both Ishkanah decks in this article are favored versus Mardu).
On top of that, the decks that Mardu is great against become less good. The more people warped their decks to beat Marvel, the worse they were versus you—U/W Flash was an example of a deck that was a good matchup for Mardu. Now with less U/W Flashes, you'll have less good matchups.
There's definitely a chance I'll end up being wrong—Mardu is a very powerful deck, after all, and Gideon is still absurdly strong—but my inclination is that Mardu will be a loser from this process.
Overall, I'd consider the Marvel ban a positive, at least as far as the Standard metagame is concerned. It opens up some interesting new possibilities and the worst case scenario of "Mardu and Zombies are too good and beat everything else" is still better for me than "Marvel is too good," since the game play with those decks is at least interactive.