Sorry to "read" that.I can confirm that.
Before the Oreo update I lost around 3-4% of charge over night, now it´s at almost 20% without anything obvious draining the battery. The phone is in deepsleep all the time...
Samsung knows how to ruin their devices with firmware updates.
But since october Im having this exactly same problem even with the nougat .
I dont know whats going wrong with Samsung updates or my phone, but then issue appear after an update.