Very good write up and discussion. I also think Mentor is to powerful to not be restricted. The answers to Mentor have minimal impact as where vs Shops (when Lodestone was not restricted) 1 Pulverize could destroy the entire Shops gameplan. Where Dread of Night/Illness in the Ranks can be answered by Misstep, bounced with Repeal and have no impact on the rest of Mentors gameplan. I dont think Gush should be the target of the restriction, it should be Mentor.
Also, lets say we restrict Mentor, does this just open the door for Pyromancer to be too powerful? I actually dont think so. The card relys ONLY on Instants and Sorcery spells. Mentor gains value off of every spell in the deck besides lands with pumping itself and generating other creatures so the card advantage is not equivalent from Pyromancer to Mentor.
What I could see happening with Mentor restriction would be a solid meta of...
Shops (making a comeback)
Pyromancer/Delver (Delver could be playable again)
Storm
Dredge
Big U decks
Oath
All of these decks play very well off of each other. It has diversity and your SBs can be evened out in a great way to strategize against the field.
Doesn't that look more healthy than MENTOR.FORMAT? I dont know, maybe its just me.
@diophan Thank you for this. I sadly may not be able to make Eternal Weekend, but if I can, the fact we cannot test the new cards from a set before the biggest tournament of Vintage of the year, is very dissapointing. And for someone who can really only test online due to work and the fact we invested $ into mtgo, I'm confused on how they don't have a sense of urgency on this. Thank you again and I hope this gets the ball rolling.
Tom
@diophan Ryan, Rich is correct. You'll need to adjust all of these to say UWR. I don't know what "jeskai" is
@Juggernaut-GO thank you for this post! i HATE Mentor and I will try any way to beat the hell out of it.
Mentor is the problem, not Gush. Leaves the Mercadian Masques common alone 
Awesome and thank you, Matt and Ryan for all of this info. It's greatly appreciated.
I feel like restriction of Gush is coming, so for the next daily events I get to play in, time for a GUSH PARTY!
Great write up, and still bummed I couldn't make it, but I'll be there next year
Not surprised to see no Pyromancer's in top 32, Mentor is much more powerful and consistent which annoys the hell out of me.
Not sure if people are still trying Grixis Pyro but to me since NYSE the deck is to slow not being able to keep up with Mentor and W Eldrazi which is another tough MU.
I also heard so much excitement over Leovold and Daretti. I thought Daretti would make a huge impact, but I think a Grixis Thieves/Control deck is also to slow vs Gush and all of the Sphere decks.
Leovold I was never a fan of, I thought he had no impact vs non U decks and the casting cost of BUG is difficult to assemble consistently
@Trius I'm not sure why you're directing anything toward me...
My comment was strictly to Matt just letting him know how the finals went.
Most decks throughout all formats are "stock" with the data everyone has.
Currently in Vintage, if you really want to take down a tournament you should play Mentor or Shops. If you want to play another deck, go ahead.
Out-
Bolts
Pyroblast
JTMS
Grudge (leave 1 in for Hollow)
Probe
Basic land (depending on the build)
those are the cards I typically cut.