As most of my friends in the Vintage community know, I don't usually get involved in heated debates like this, but I felt like I should add my opinion in for this latest installment of banned and restricted debating.
To me, there is one big problem that can often occur when discussions like this get going: personal bias. I think that it's important to try and look at the format from an unbiased and objective standpoint. There's been a lot of debate about Workshop decks in the past few weeks, but I personally feel like they shouldn't really be a major target for any sort of restriction. People have a lot of strong feelings about Workshop decks, as both pilots of the deck and opponents of the deck, but I truly do not think they currently warrant a new restriction. Workshop decks are unquestionably powerful, but with Chalice of the Void's recent restriction, not unfairly dominant. While I have my own opinions and observations about Workshop decks and the mighty Lodestone Golem, that's not what I wanted to focus on with my contribution to this thread.
With all of that said, let's take a brief look at the recent history of Young Pyromancer and Monastery Mentor, which is where I feel the real "problem" of the format lies.
When Young Pyromancer was printed, Vintage enthusiasts were intrigued by the option to play a cheap creature that grew horizontally as opposed to growing vertically. What this meant was that, even if an opponent dealt with the Young Pyromancer itself, it likely still left some value behind (in the form of tokens). This was an obvious improvement over cards like Quirion Dryad and Psychatog. Young Pyromancer was quickly respected as a powerful card. Its presence began to define popular decks, working well with cards like Gush and Cabal Therapy. It was a great "finisher" card that was both controlling and aggressive.
In 2014, "RUG Delver" began to take over the Vintage metagame. When Treasure Cruise was printed, the deck was at the height of its superpowers and everybody was either playing it or coming up with ways to combat it. At this time, I was trying out a RUG Oath of Druids deck that featured Slice and Dice alongside 4 copies of Volcanic Fallout. (Great with Forbidden Orchard!) It didn't take long for both Treasure Cruise and eventually Dig Through Time to be identified as way too powerful to roam free. Too powerful for what, though? Delver of Secrets was a good card, but it was Young Pyromancer that was ultimately benefitting from all of the card draw and card selection. Other decks obviously benefitted from the "delve duo," but the "Delver" decks were abusing them the most. An Oath of Druids deck won 2014's Vintage Championship, but it was one of the few in sight among the top 32. A good portion of the other top competitors were piloting some sort of deck that featured Young Pyromancer's power.
This brings me to my favorite moment from the old TMD forum. Ethan Fleischer, a Magic designer and developer with a personal interest in Vintage, posted this comment:
It was funny but also appropriate and accurate. At the time, Young Pyromancer was dictating what we played, how we played, and ultimately what should be restricted within the format. It was the quiet puppeteer behind the curtains. Sure, Treasure Cruise was (and is) a good card in any deck that's playing an Island, but it was highlighted by Young Pyromancer's dominance. It's important to note that, at this time, Gush was considered a powerful and useful card, but not something that could warrant a restriction. Fleischer's comment (along with Treasure Cruise's restriction) was a public admission from Wizards of the Coast that Young Pyromancer's dominance wasn't going unnoticed.
What is especially important to me about Fleischer's comment, however, is that it was made just mere weeks before Monastery Mentor was printed. This is where it all gets confusing for me. Young Pyromancer was completely acknowledged by all as a powerful and format-defining card. There was a ton of data to support this, and yet, the design team responded by creating Monastery Mentor, a creature that was far superior to its now long lost little brother.
Young Pyromancer, though wildly powerful, has a lot of problems. It has no inherent way to protect itself. The tokens that it generates are the "lowest of the low" when it comes to a creature in Magic; they're 1/1 elementals with no built-in abilities besides being able to attack and block. Young Pyromancer is also just a 2/1 that dies to basically everything. Whether it's Engineered Plague, Lightning Bolt, Toxic Deluge for 1, or Fire//Ice, it's an easy target. Heck, even blocking it with a 1/1 such as Cursecatcher was a guaranteed way to kill it, which is why Young Pyromancer often didn't attack or block if the coast wasn't clear.
Outside of costing a single extra mana, Monastery Mentor is superior in every way. For starters, being a 2/2 instead of a 2/1 is a nice plus. Young Pyromancer took over games just by generating tokens off of instants and sorceries. With Monastery Mentor, it now benefits from every non-creature spell. With cards like Sensei's Divining Top and a full suite of fast artifact mana, this subtle difference makes for a huge bonus. Not only does Monastery Mentor create tokens as its controller plays spells, but its power and toughness also grows. As we know, direct damage (outside of Sudden Shock) isn't a foolproof way to combat a Monastery Mentor. This monk creates ludicrous board states before its opponents can even blink. It's dangerous in the present and way more dangerous in future turns. The icing on the cake is that, even if the Monastery Mentor dies, the tokens still grow without it. They're all just as dangerous. Unlike Young Pyromancer's lame duck tokens, Monastery Mentor's tokens do serious work. I personally feel like the tokens, flavor-wise, should require the original creature present to grow, but they all flourish on their own. How could research and development possibly give the "OK" for this creature to be printed with all of the existing data from the past year? This is a rhetorical question, but I actually have no idea how this possibly happened.
Why am I bringing up all of this? It's important to look at the history of this "token era" and understand the effect that it's having on our metagame. Due to increased token dominance, Gush has become a topic of restriction discussion, though I feel like Gush is a nice part of our metagame that wouldn't be noteworthy if Monastery Mentor had stayed as Young Pyromancer. Young Pyromancer was wildly powerful, but fair. In my opinion, it was a really nicely designed card that balanced somewhere between "average" and "out of control." Monastery Mentor is such a crazy improvement that it makes otherwise normal cards like Preordain and Gitaxian Probe look busted. I've actually heard people debating whether either of those cards deserve a restriction, which truly shocked me, as I view those two cards as very mortal and underwhelming in the grand scheme of things.
So am I suggesting that Monastery Mentor gets restricted? Not necessarily. I do, however, think it's important to look at the Vintage metagame as a whole from the perspective of these two cards and how they've shaped Vintage over the last two years. They have mostly homogenized blue decks while also making average cards look back-breaking. Even with Gifts Ungiven and Thirst For Knowledge becoming unrestricted, it's still all about this new token-generating "cantrip" breed of deck. In my opinion, Monastery Mentor was a printing that made no sense. It dramatically improved on an already existing powerhouse that didn't need help. I've joked that it is the most puzzling printing since Memory Jar back in 1998. From an objective standpoint, I actually think the token-generating concept is a pretty cool (and obviously powerful) strategy, but it has now become way too efficient, automatic, and format defining.