Well, you've also wasted your only frost (it's unlikely that you'll have 2), and it's very hard to beat monsters without it. Also, if you played your 9pt spy, it might very well be the one that stays on the board.
Huh? If it stays on the board you don't get 2 cards. It just stays on your side. And yes you have muster but the point is I have 1-2 more cards than you. You can never risk passing in that second round. So I continue to play my lower level cards till you have none left. I win the last round and the game. Who cares if you won the second round by 120-50.
That's why the monster deck is not that good. I don't think I've ever lost to any of the AI gwent players that used the monster deck. As long as I have at least 1 spy and 1 frost (don't need a second one and in fact don't want it) card I'm guaranteed to win.
Here's the bottom line:
1) I'll win the round where I play frost.
2) I have more cards in my deck as long as I get 1 spy more than the monster deck.
These two items guarantee a win.