Post Rotation:
It can win against all matchups if you are smart, except Fire. However, Fire isn't good against most decks, because it needs abilities, has bad starting Pokemon, and loses Blacksmith which was one of their best cards. It also gets squashed by Mega Ray, Groudon, and Mega Mewtwo. With Rayquaza you just have to make sure they can't bench more than 7 Pokemon (easy), and then you out grind them. With Groudon you win with type advantage and speed, and against Mewtwo, you just have to be really smart with energy placement. The issue with the deck is that is requires a lot of resource management, which few people are willing to do. The deck can be cloggy, but so can all decks. I think it can be viable in the hands of a good player who takes the time to learn the deck. I have made a lot of posts about the deck and their has been a lot of discussion on this forum, so if you want to learn about the deck, you can.