The win ratio is currently 55:45 between Alliance and Horde, for the last 50 hours. We believe the win ratio will remain like this, or possibly even improve. Like it was mentioned, we were not trying to improve the win ratio with mercenary mode but to address queue times. Win ratio was not that admirable before mercenary mode either. In fact, with our latest changes it's better than it has been for a long time.
The way we see the picture is a bit different than players. While a player might personally feel like they're losing all the time, we can actually see the number of wins and losses per faction. The reality is that crossrealm and mercenary mode didn't do much to change the win ratio which was not Horde favourable before either. It helped though for a majority of players to notice this. We cannot do much about this situation without going into deep custom changes that would change the meta of the game entirely. However, we can improve the mercenary mode so it rather improves the overall situation.
Our change, you can already find on your account panel on the website. It is an opt-in so you can participate in mercenary mode if you desire. If you do not wish to participate in it, you can disable it. It is turned off by default.
It can take 60 seconds for the changes to take effect and you must be logged out. Due to the reality of crossrealm and our update schedules, it might take a few days before all the changes are live on all three of our realms. Queue times should remain short.