Brought the phone out (went to alab to replace my f-ed up lightning cable) and checked the battery life. Non stop use for the 3 hours to-and-fro battery life from 100% down to 44%.
Feels about the same as 8.0.2.
you tried that lightning cable with other iphone and is it usable?
my previous iphone 6+ symptoms;
1. battery drain really fast and charge very slow
2. original lightning detected as not supported <- !!!
3. Diagnostic on battery reveal 100% health and no issue
I think your case might be similar to mine. Culprit was the charging port.
Bought 12w adapter to try to "jump start" the battery but still shitty. End up bring to QCD and get 1-to-1 replacement.

