Just to chime in here, i have been having the same problem on my S 8.4.
SO i sent it back to Samsung.
The device was rooted, with a Knox trip, but was running stock rom.
I sent it to Samsung UK centre and have received an email back today from them, saying that it is out of warranty.
And they require £97 pounds to fix the fault.
"Thank you for sending your Samsung SM-T700 for a repair with us. Your item has been examined by one of our engineers and we have found that it is not covered under the manufacturer’s warranty.
Please see the attached quotation raised for the repairs. Also attached is a picture of the damage located on your Samsung product. We hope the picture helps explain the damage we’ve located."
THe damage they say they have located was a photo of the charger port.
Bear in mind i sent the tablet fully charged to them, and although a bit tight the port is fine and fully functioning.
So i called them up , and explained that the port is fine, the problem i have is the rapid battery drain - The battery , not the charging port.
I was told that the damaged port would need to be fixed before they would look at the main problem.
I feel a really fed up tbh about it. I would of happily & kind of expected it to be turned down due to Knox trip, however the fact i'm being charged for something that really isnt a problem winds me up.
I said that i wouldn't be paying for that, the tablet charges fine, its only a month old and will have it back please.
I guess my next move is take the back off. Left a sour taste in my mouth though, my house is full of samsung stuff.