Originally Posted by
Menteith
Briefly, as I feel like we've gone afield of my original point;
(I believe) that 12post/Breach Post couldn't speed itself up significantly. I also believe that the deck couldn't significantly increase its protection/disruption without damaging its mana base or threat base, both of with were fragile. Most lists couldn't function with greater efficiency than a sealed deck without resolving Primeval Titan/Green Sun's Zenith, both of which are vulnerable to countermagic. Beyond (maybe) Beast Within, the deck cannot proactively stop problem cards, of which there are many. While the deck was indeed a reasonable choice against slow control decks that refuse to make metagame alterations (as I consider Pyromancers Ascension and SplinterTwin, depending on build, to be control decks with decent finishers as opposed to combo lists - anything packing both Mana Leak and Firespout seems like control to me), I don't believe that it could have been significantly improved enough to deal with the metagame that emerged.
Now, I could have been wrong. Maybe a piece of tech would have emerged that fixes the deck's problems against fast aggro, or makes it more robust against disruption (random note - back in testing, I found that a single Cranial Extraction in a black deck with Beseech the Queen to find it would basically win against 12post). There might have been a card that both doubles as acceleration and protection that no one noticed, or some other unlikely situation. But the deck wasn't an unbeatable juggernaut that forced everyone to run narrow cards maindeck to beat it. The metagame had clearly adapted to the deck, and had found ways to beat it down already, without Wizards making a single change. And I think that letting a metagame find solutions (and I'm not even saying it was a problem) is a much better choice than making sweeping changes on some very limited evidence.
Look, Solidarity represented a hardcap on similar style decks for a very long time in Legacy. Counter heavy control decks with slow win conditions, or unprepared control decks in general had huge problems beating it. This wasn't inherently a good or bad thing, and Solidarity was for a long time a pillar of legacy. I think that solutions to 12post would have been found, just as solutions to Solidarity were found without the heavy handed actions of the DCI.