Someone posted the stats from another thread of the qualifiers, and the stats tell quite a revealing story about MO.
When MO go first, they had a winrate of 70%, but when they go second they have a winrate of 37%. That is a MASSIVE variance, very unhealthy for the game.
It seems to me that the MO cards aren't broken, it's thrive that has become broken now that MO has gotten some quality pointslams. Before, building up thrive was difficult, but now that monsters have powerful pointslams later on it forces opponents to react quickly to Endrega Eggs, Nekkers, or Self-Eaters (although just a relict thrive), because these cards if left unanswered early on will carry away the game.
Conversely, when MO go second, they get crushed because opponents have a chance to put down removal engines onto their board or develop their board, making it impossible to get the thrive steamroll going. Without the early game thrive, reaching later sabbath becomes very difficult for MO and they lose hard.
If MO have their new cards nerfed they will go back to being trash, but if thrive is instead looked at and modified so that it's not simply go first or lose, I think the MO problems people are having will be solved. Right now, it's apparently a coin toss for MO.