Gmg has no real control over what valve and Warner choses to do about this. They just buy and sell the keys themselves. They don't actually have any control over activation and revocation of the keys in order to issue refunds.Like with GMG, you guys need to kick up dust to make sure they hear you.
This is why buying from key sellers is a double edged sword in cases like this, and it would be wise to remember next time you see a game that's 30%+ off on gmg vs steam.