Update: Apple confirms they screwed up.
We did what would could to prepare for Apple’s release of iOS8; We’ve had an Apple Caching Server up and running for months. We expected to fade the new release without a hitch. But instead, Apple did something that appears to have disabled caching of the iOS8 update (see this Reddit comment in this Reddit thread, we observed the exact same issue.)
What did we do? Blacklisted the two update domains, mesu.apple.com and appldnld.apple.com in DNS.
It’s a shame we have to disable updates in order to maintain bandwidth order but c’mon Apple, why did you break the caching server?