I seem to be one of the only people here having the most serious problem described who actually fixed it himself. I suspect that there are multiple wacky reasons why these phones are draining their batteries so quickly, so I'm not promising anything, but Apple's solutions (DFU restore, get a new phone, etc.) are not addressing the real problem. I encourage you to consider:
1) Are your Usage and Standby times in Settings/General/Usage virtually the same? If so, the problem is that your phone is never going into standby. That would explain the battery drain.
2) In my case, my phone and my iPad had the battery problem, got better, and then had it again - with the problem starting and stopping simultaneously on both devices. I realized that it was the iCloud bookmark synchronization process that was keeping the iDevices awake. On my desktop, the Apple IE DAV process was churning away constantly, even though I hadn't modified bookmarks in days. On my iDevices, Safari was registering 1 MB of usage every couple of minutes even when it was closed. When I disabled IE syncing, it fixed everything.
I'm not saying that this is precisely the problem on any given phone, but do try things like turning off Wifi, resetting cellular data statistics, not using the phone for a while, and then seeing what program or service is most active. You may be able to pinpoint what is keeping your phone awake all the time. In my case, I could do something about it, and now my little machines work and I don't have to be anxious waiting for the next iOS update.