I'm not specifically talking about Pro Ladder, but yeah, I've noticed similar. I don't know if there are some hidden algorithms Gwent matchmaking then considers when pairing. This is just a casual observation, but some decks/factions (others which I have more wins than others), take longer time searching for opponents. So there might be something more than meets the eye here. And that's fine, IF that's generally beneficial, but it sounds like in your case it could really be problematic.