So, I think I figured it out. It seems to be a bug in IOS 8.0.2. Here goes...
In “Settings”, under “Fetch New Data”, it used to be that the Exchange account defaulted to syncing ONLY the Inbox. Now it defaults to syncing the both the Inbox AND the Sent folders. The bug, as I see it, is in the fact that in addition to this new default - it now WON’T let you turn off syncing the Sent folder. If you go in and uncheck it, and then go out and back in – it’s checked again. Furthermore, regardless of whether you change the setting for this account to be “fetch” (rather than “push”), it still tries to sync the Sent folder. So, if under the account setting you have the “Mail Days to Sync” set to “no Limit”, what’s happening is the phone is busy syncing EVERYTHING from your Sent folder (for me this is over 170k items!!!). So, the phone (and the Exchange server) are so busy dealing with all of these requests that it APPEARS to be locked up when in actuality it’s just taking a really, really, really long time to respond back for your Inbox requests (ie: this is why it loads the headers but takes forever to load the body of the email once you drill down into it). This is why the
download syncing spinning wheel up on top is constantly going and the battery is getting drained so fast.
So until Apple fixes this, here’s my workaround:
Make sure your “Mail Days to Sync” is a small enough time period (ie: a week or two) that your Sent folder sync gets done quickly after setting up your account (ie: maybe a couple minutes). Once the Sent folder sync is done, the spinning wheel up on top should go away and your response time (and push emails) should work fine again. It did for me.
I’m curious to see if anyone else finds this works for them. Please let me know… And good luck!