Same problem here. Except my iPhone 6 PLus saw it and even downloaded it at Boston Market while eating and early lumch <ha> It was done in just minutes, but when I got home nothing was showing for my iPad mini 2 or iPad Air 2. You can grab the actual update from the developers site, but if you do it that way it WILL erase the entire device which I just found out.
So I followed the instructions that someone on here said to do:
Go to Setting -> General -> Profiles
and delete the IOS Beta Profile (I guess it was from beta 2 or maybe even from 8.4 beta I don't know which), restart your device and VOILA there is your OTA update.
Wish I had known before I wiped oit my iPad Mini
Grrrrr