Although there's a lot of good information in that article, (I was reminded I need to install an ad blocker, safari for an hour a day can easily be 50% of my battery usage) I was astounded to not see any mention of bluetooth. I turned that off a month ago and noticed a massive improvement on battery life.
With my old iPhone 4 I would have agreed with you wholeheartedly about the effect of bluetooth on battery life, but I now have an iPhone 6 Plus and my wife an iPhone 6 and both of us have Apple watches. Because the Apple watch loses 95% of its functionality without a bluetooth connection to our iPhones, we never turn Bluetooth off — except when we turn on
Airplane mode, which we do using the Apple watch (I still have not figured out how the watch turns Airplane mode on the iPhone off when Bluetooth is off, but it does???).
The point is, as far as we can tell the effect of bluetooth on battery life on our iPhone 6's is unnoticeable. My only explanation is either much more efficient Bluetooth transceivers (it almost has to be to work in the Apple Watch), perhaps an ability to switch to a low power mode except when actually transmitting or receiving data, or maybe both.
