Hate to break it to you but the Day 2 statistics http://magic.wizards.com/en/events/coverage/gppit15/day-2-metagame-breakdown-2015-11-22
and the Top Eight do not back up the claim. Three Twins, two Affinity, and one each of Scapeshift (nicely called Sheridan), Grixis, and GW Hatebears is not a Combo Winter scenario. The combo decks that did the best here are all the “fair” combos. And GBx did take 1/3 of the undefeated slots Day One. Looking at Day 2 Amulet Bloom had a good showing but dropped off precipitously and Grishoalbrand was a very small percentage. If I were to guess, the coverage team went for the most unusual decks to showcase rather than the Jund matchups that we’ve seen hundreds of times. I expect that we’ll be seeing a lot of pro’s complaining about their deck choices and how they Next Leveled themselves rather than play the deck they knew.

Playing a deck with Path to Exile and Mana Leak remains a losing proposition.

I don’t disagree with the assessment that jund is more flexible; but there is a certain class of player that prefers reactive flexibility to proactive flexibility, and those include some of the best players in the history of the game. There’s a reason McLaren consistently does super well at large modern events playing UWR variants. I also want to point out that the UWR deck does have a long pedigree of being a reasonable choice in the modern metagame; it hasn’t been out of tier two status for THAT long, and it certainly spent more time in tier two than many of the decks currently there. I will also point out that the last time they did a deep-dive in modern, UWR control was actually one of the best decks when piloted by a skilled player–I seem to remember the number was something like a 67% mwp overall for the better pilots, which is insane–that’s comparable to the best HOF players at their career peaks. Do I think it’s going to be a big part of the metagame? hell no. Do I expect to see a couple of good pilots break day two and a VERY skilled pilot break top 16? I wouldn’t be surprised.

I’m not arguing for it to win or make a big impact, but it is probably my top choice deck to put a skilled pilot into a good finish.

I should have phrased that differently with some specific numbers, because it has lots ground from its summer shares of 8%+. I didn’t include that though, which is my bad. Also, I actually think a flat 0% change for Burn within this period is a form of losing ground. It’s not as if all the other linear players just transitioned over to the easy Burn pick, which is something we see in more open metagames. Definitely should have been more clear about that, but it’s very interesting that Burn has hovered around that share for the last few months and hasn’t gone up since.

I’m going to disagree with you completely.

1 – UWR has always had this flexibility, but it’s flexibility never gave it the same 50%+ against the field that you see for Jund.

In fact this whole comment describes Jund better than it describes UWR. Jund is the flexible deck in the format.

2 – Grixis arguably has better removal (Terminate over Path), a better man land in Creeping Tar Pit and access to Kolaghan’s Command. UWR gets Lightning Helix and better sideboard options.

Perhaps a better argument is that UWR is better positioned against Zoo/Company decks, not sure if that’s true buy I wouldn’t argue against it.

3 – I play UR Twin, I always bring in my Moons against UWR. Blood Moon wins games against UWR. If you’re expecting Blood Moon, I wouldn’t play UWR.

4 – nobody is gunning for control, but they are gunning for Twin and Scapeshift and you’ll suffer the splash damage. Also this argument has been argued to death for the last 3 years, and each time UWR fails to deliver.

Unfortunately the deck is just missing something and I’m not sure what it is. But the problems I see are:
1 – it’s greedy mana base
2 – it’s slow win pace (the deck just doesn’t change gears fast enough)
3 – there’s no Tasigur/Goyf equivalent in UWR – the closest is probably Restoration Angel, which can be dropped end of turn.
4 – a reactive game plan, which is currently the death knell for decks in Modern. This is because in an open field you’re going to need a proactive plan in certain matches. I call it the “free win theory”, if your deck doesn’t have free wins then it’s probably not going to do well.

Tag didn’t appear–now it has my handle attached to it.

1. UWR is one of the few decks to have real flexibility in an open metagame–the primary school of thought in modern is that robust power is one of the best bets in an unknown metagame, but there is a class of player that prefers flexibility over raw power.

2. Spot removal is at an all-time high in importance in modern–UWR and UBR are the two wedges with the most robust removal suites, but UWR has better tools for abusing sweepers, which are also probably strong at this event. More to the point, UWR is more likely to have hard sweepers in the mainboard, and it certainly has the most flexible/powerful sideboard options.

3. Bloom/Twin/BGx are all running fairly high at the moment–I see this as conditions for more blood moon effects in the metagame, both because players see twin performing well and shift to it, and because the perception is that bloom is on the rise AND fairly weak to blood moon. Regardless, higher prevalence of blood moon as disruption means that URx shells start to have some natural advantages in the format because they aren’t *as* weak to blood moon to begin with, and blood moon pushes out other sideboard options that can be more hateful to UWR.

4. Nobody is gunning for control. This isn’t 2012 anymore, UWR isn’t a top tier deck; with the race to the bottom in terms of speed and noninteractivity over the last few months, people’s sideboards have scaled back to interact with those decks and control hosers are at an all time low in modern sideboards.

One minor comment: you lump Burn in with other aggro decks as losing ground, but it’s stayed exactly level at 7.8% according to your chart. This doesn’t surprise me too much, as looking over the meta game and the deck lists I can get ahold of from major events, there’s not a ton of hate for Burn match ups right now. Jund and Junk decks, for example, appear to be largely stepping back from Feed the Clan (a massive burn hoser), instead opting for softer answers such as Kitchen Finks and Timely Reinforcements in the board, which are MUCH easier to manage with Skullcrack/Atarka’s Command. This is perfectly reasonable; why target Burn, which is 7-8% of the meta, when Affinity is a massive 12% of the meta, but it certainly helps Burn’s match up vs those decks. In general, the meta seems decent for Burn, with only Bloom Titan being a noticeably bad match up and plenty of even or slightly favorable match ups (depending on deck builds and SB choices) in Twin, UBx, and Tron.