They’ve designed midrange out of existence, though. There are the occasional outliers, but decks are overwhelmingly either pure aggro or “here’s five lethal-thread boards, clear them all or die” or outright OTKs.
I’m not sure if it was the best deck even then. Questline Warlock started off as a monster. But at first, yes, it was tier 1.
Then they nerfed it to Tier 2, and people still kept playing it. So they nerfed it again, even though the expansion released Questline Warrior upon the meta in full force and that shift by itself had already reduced Questline Mage to Tier 3, so the nerf took it to Tier 4.
Then the mages just switched to the Tier 3 Mozaki and were still around. You can’t get rid of Mages with nerfs, they have diamond hands.