I haven't read the entire thread, first few pages and last. I was in a panic about my iPad air 2 and 6+ battery.
Previous ios update, thought I was imaging things, my battery life was much shorter, and to top it off, couldn't understand why my Verizon data usage on my iPad was double what it's been for a year and a half, costing me a lot of money.
Latest update, my ipad was battery was draining even on the car charger. I use it 4-6 hours a day for maps and navigation, which of course uses a lot. However, I used to be able to go all day without plugging it into the charger. Since the new update, it's down to 40% in an hour, plugged in! Yesterday, after reading somewhere on page 1, someone turned off iCloud, so I did. Turned it off. Battery was back to normal today, forgot to plug it in until I noticed it was at about 85%, it charged up while in use to about 95%.
My iPhone doesn't get used much unless I'm travelling. Normally, charged it every 3-4 days. Had it plugged in last evening, it was 100% this morning, didn't use it all day until about 2pm, it was down to 16%. Remembered That I didn't turn off iCloud on the phone. I have now, for sure.
Further reading up, may not have to turn off iCloud, just "use cellular data" under iCloud drive. I'll try that tomorrow.
UPDATE: Having iCloud drive on at home on wifi with "use cellular data" off, doesn't eat up my data (cause I'm on wifi,) but the battery still drains rapidly unless it's plugged in. Took it off the charger to use it in another room, (just the calculator briefly, then just put it down.) Picked it back up about 20 min. later, and the battery had gone from 100% to 74%.
So, I'm turning iCloud off completely, unless someone has another fix that I haven't found yet.
(Just in case anyone is wondering, have unlimited data on my T-mo iPhone, but I've had my iPad on Verizon because 1 gig and $20/mo. has been fine, and in many areas I go thru, don't always have T-Mo coverage, where I might still get Verizon. I go thru a lot of rural, middle of nowhere places, and sometimes don't get coverage on either.)