I'm also seeing battery drain between 40-45% since upgrading the fb app yesterday. I tried deleting and reinstalling it hoping maybe that will help. I've also completely disabled location services (before I had it set to "while using the app"). For many versions this app has shown background app usage despite being disabled for background app refresh. I think this last version is the worst I've seen with battery drain. One thing to add would be that if the app is running in the background regardless of background app refresh, it is may also be using location services "while using the app" because it is being used in the background. I'm hoping disabling location services helps.