Since the new release, my multiplayer rating has been going up without reason. I have only played ranked once ever, and that was before the release and it brought my rating to 306. Yesterday, however, I logged in to find that my rating was at 500-something, and after a couple of league games it was 600, and I thought for a moment that league wins were changed to count towards that. But then, my rating was not changing with every league game, and when I logged in this morning it was inexplicably at 723. My in-game list of matches confirms that I have only played league games, so it's not like I've encountered a benevolent hacker who's good at multiplayer.
This was in the latest build: Renown goes up for every 3 MP games, not 5. Renown and game counts are increased from league games. However, that wouldn't explain the mysterious raise in rating, unless it's tied to the renown gain somehow?
Yes, there's an issue here where league matches are affecting the rate at which your MP rating increases. I'm going to fix it in the next build.