I have been having some huge battery drains (woke up today to a dead phone) and it seems to be the Apple music app.
All the more reason to not blindly leave apps in the app switcher. You never know when they get hung on any process and cause performance issues. Facebook and the new Music app cause all sorts of things when left in it.
I know it's been talked about to death and people will say over and over again that you don't need to close out apps and it saves battery because they don't need to launch fully when left in it. But those battery benefits Do not last as long as people think. Most apps can get an extension to run in the background for a max 15 minutes to finish a task. After that the app shuts down. If you're doing a lot of other things within other apps, odds are you've tossed that previous app out of ram already. And it would require a full launch again anyways, negating the benefit.
So really if you're not using an app multiple times an hour or at least once an hour, on the hour, it would be safer to just close it out after use. This prevents apps to get stuck without knowing causing one to think it's the OS lagging and stuttering and is the worst OS ever and iOS 6 was sooo good, when it's some random app hung up causing it.
Sure you "shouldn't" have to close out apps. But with the millions of apps out there, by big companies or small there is no guarantee they will all run perfectly all the time. Personally I rather have the control and keep it lean, that way I know if something funky is happening there are only a few possibilities to what's causing it.