Yep, same here. I've been doing nothing with my Galaxy 6 for the past month while it drains 2-3% per hour (used to be less than 1% per hour). If I do anything with it, e.g. the radarscope app, it drains close to 20% per hour (used to be 3-4% per hour). So I don't do anything. Even phone calls use 3X the battery they used under marshmallow.
Here's what I have done: run battery monitors like GSAM. Those tell me the drain is from failing to doze. Also the extra battery drain is "System idle" and "Android System". I have factory reset. I have tested without cell service, without bluetooth and without wifi (all separately) and there is no change. I have many cache cleans. I have reset all settings. I run in safe mode and "ultra" lower power mode which stops many apps and there is no change. I cannot fix the problem or even diagnose it.
The Sprint forum people told me to go to the Sprint repair store. I went and they reflashed nougat (they would not or could not go back to marshmallow even though I pleaded for that). There was no change in power drain. They blame my apps (not true), my hardware (why did it start the moment I installed nougat?) and my battery age (same question). They noted my cracked case and said it will be $250 plus undetermined hardware costs to fix an unknown alleged hardware problem. They are more than happy to sell me a new phone.
All I can say is ignore anything anyone says unless it is not in my list (which is probably not complete). If someone does mention something new, please post it here.