Seeing there is no reply to this yet, I felt I might as well add my own perspective.
To clarify what I understand be to the subject here, you are addressing the issue of dishonest players, who create dummy players to play against, in order to gain effortless Wins and increase their rank on the leader bard.
The problem with this issue is that there are no efficient ways for the games to detect a dummy player and its owner. Hypothetically, it could be possible to make it more difficult to play against a dummy player, if the games would take note of whether the dummy is scoring any points during a match, and then close the match if the dummy does not show any sign of activity (I don't know whether this may actually have been implemented already). But if the owner of a dummy player is operating both computers during a match, there really is no way to identify the dummy, because the circumstances would be the same as that of two authentic players having a match against each other on the same network.
I understand it's frustrating to watch this kind of fraudulent activity take place in the lobby. The only way to address it would be to manually evaluate the stats of a suspected player. But even if a player were to be suspected for milking a dummy player, it would still be difficult to prove the fraud, as any dummy player could technically be confused with an unskilled player, having few to none Wins and several Losses.
It just seems that this issue might be an unfortunate vulnerability with this type of opponent-based gameplay.