Although we highly prefer to avoid making changes to our banned and restricted lists and let, instead, the metagame adapt to temporary unbalances, some archetypes and colours have clearly dominated the Old Frame Vintage format for the last few years, with no sign of it changing.
As of today, since we restricted Merchant Scroll, there have been 13 online Old Frame Vintage leagues and 13 live tournaments. Out of all those 26 events, 24 of them were won by decks that played 4 Brainstorm. The only exceptions were the Online Old Frame League VI, won by Tools and Tubbies, and the first Liga Madrileña de Old Frame event, won by Sligh.
Players need a very good reason not to play 4 Brainstorm while staying competitive. In every event there have been participants trying different archetypes, some of them targetting blue decks very heavily, even playing cards like Chains of Mephistopheles main deck. But decks featuring Brainstorm have kept on winning tournaments.
The fact that all of these 26 tournaments have been casual also deters most people from putting the effort to innovate and bring some opposing deck that could potentially perform well in a blue-dominant field.
We find this situation to be very similar to when we restricted Merchant Scroll. Both cards could be played as 4-of in Vintage when Scourge was released, as most players were not taking full advantage of their power. Fetchlands had been printed just a few months before and in those days it took players longer to make changes to their decks, so Brainstorm was not that popular.
However, as was the case for Merchant Scroll, it also ended up being restricted. So we consider that this change is also backed by history, even though our format is not identical to what Vintage was when both cards were restricted in June 2008.
We think this change should increase the number of competitive options that players have, by lowering the power level of those blue decks that are clearly doing better than the rest.
We acknowledge that The Perfect Storm and other storm variations like Pitch Long, Doomsday, or Drain Storm have performed better than any other play style so far. By restricting Brainstorm we are also targeting those decks specifically.