Steamcharts is saying otherwise, the concurrent numbers have gone up since the patch. The reason you are seeing "so little active servers" is because a lot of the players who were previously getting stomped are now all on Novice servers together, which you do not see in the server browser unless you are a novice.
That a large proportion of the active playerbase was being split off into novice servers is the reason why they had to merge Frontline/Invasion, and while the Novice servers exist, they can't go back to unmerging them.
This is pretty much it. That said we are aware of the current issues, and are looking into ways to improve them with e.g. a better voting screen that is weighted towards invasion.