Well, when you think about it the OS is what's doing all the work, so other than perhaps the screen I'd expect it to be near the top of the list. GSam shows a slightly different breakdown of battery usage
//uploads.tapatalk-cdn.com/20161028/a9da17453854592a05f6ea1158e9528d.jpgbut the important thing is really: are you getting a reasonable amount of screen on time for the total time since the last charge? If you're getting 3 to 4 hours of screen on time before getting down to 20% charge, and the Awake time closely matches the Screen on time in the History details, then that's probably all you can expect without looking deeper at wakelocks, etc.