I have the same issue as well.
I wish apple would at least acknowledge this.
I updated my 5s on the day ios8 released to test everything before telling anyone else it was good.
my phone was doing exchange 2010 active sync until Saturday morning it stopped syncing my mail.
I stopped by the apple store on Sunday morning and nothing is fixing this.
I removed and added back my account from owa, I tried the Wi-Fi on and off tricks, I tried downgrading and it still did not work, many restores and still my 5s with ios 8 as well as a handful of other people who updated are stuck where the out of office says loading.
I got 2 new iphone 6's last week and I get the same result on them as well.
what is funny I have an ipad retina hd and I updated that with ios 8 last week and it is still working on exchange server with no problem.
anyone looking here should look in setting exchange account for the automatic reply and say if they are stuck at Loading since all mine are.