Same issue here with Android OS and System contributing to battery drain.
I'm at 38% right now with 10 hours 44 mins on battery with wifi about 50% of the time
30% for OS and 16% for System; Pandora for 9% (1 hour of streaming through bluetooth on LTE)
OS shows CPU total at 3 hours 10 mins, while stay awak is at 5 hours 56 mins. System = 1 hour 42 mins CPU total. Both combine for less than 2mb used.
My screen time is 57 mins on auto brightness.
Been tinkering with the device for a few days to try to correct the problem. I like to leave my location on, but I definitely changed it to power saving mode. Also turned off location history on Google Now. Not sure if it's getting better, but definitely not getting that incredible battery life some of you guys are posting here.