I don't know exactly what the method is, but it definitely takes into account some skill level and not your current division. I've seen a lot of people complaining about the same thing, and it's definitely proof that something's going on. It's not normal that everyone's getting relegated now, losing way more games and suffering more than usual in divisions where they arrived easily.
The game keeps getting worse, the servers have incredible lag, now they've added that weird matchmaking and you have to play 24/7 if you want to complete all the objectives... This isn't a game anymore, it's a job.