I can easily replicate the problem that others have here by adding apps to the dock that are not compatible with OS3. If my dock is empty, I get equal or better than OS2. Add carrot or dark sky to the dock and I lose about 20% overnight. Take them out, I burn 10% max. Tested this several times. Both apps has background refresh on as well.
Today, my dock has only the timer, settings, activity and I am burning 3% an hour. 6th day of rotating apps and it is 100% consistent. Tomorrow if I add fantastical and dark sky to the dock, I run 8% an hour.