Grain of salt here because I do not have my N10+ yet ... but I am an AT&T user on a N9, and after an update I suddenly had this issue. Android system is draining my battery pretty heavily, even after a lot of adjustments on my end trying to resolve it. Pretty disappointing to hear it may persist with the N10+ and that it may be an AT&T thing. Figures...
Very interesting indeed. Sorry to hear it is across other devices, but really does point the finger at an ATT update. hopefully it will be fixed soon.