Turn Assistive touch control off for rescuing the battery.
My Iphone 7 plus battery is being drained much faster than before. I literally became a wall hugger 😉. I gave a complaint to Apple and waiting for it. Even I went to one of the apple store to check if it is a hardware problem. None of them worked.
Finally one day accidentally I turned off my Assistive touch control (configured it to triple click) and then onwards my phone is back. I would say it is much better than IOS 11 or 11.0.1.
I verified this by turning Assistive touch control on and off again.
I never expected this is the reason for the drastic battery drain problem which I have been facing from the past one week. I have updated my feedback with this new finding. Hope apple fixes this problem in their next beta.