Just played few games against rank 40 guy with some garbage deck, he lost 3 games in the row, disconnected as soon as the game started going downhill for him (didn't even get replaced by the AI, just straight up end of match counting as a win), and yet at the same time he didn't lose any ranks.
It boggles my mind how Stainless can't properly implement something as simple as matchmaking. In current state, they may as well remove matchmaking based on rank and just make you pair up with random opponent, that way getting a match would be much easier, and it seems like rank 20-30 are the most competitive at the moment. Really annoying that you get one proper game every one hour, the rest being playing against AI or waiting 15 minutes in queue only for the opponent to end the game on the first turn.
It's a cheat already used in Kaladesh season, i don't know how it works but both players get the victory without playing or getting replaced by ai. I know the name of a steam player using it, because i encountered him on ladder 20/30 times last season usually 2/3 games in a row every time, and every game he was always at rank 40.
Only once he tried to play against me with a Suntail Hawk monowhite deck and before my final blow he used this cheat to make the game finish without any message to be replaced.
If 1chwhc or whatever is his name is still around i don't think we will see some action against them.