1. Reset all settings (settings app-> general-> reset)
2. Go through initial setup steps (lang, wifi, siri, enable location, etc) and choose setup as new phone (don't worry your apps, data, contacts, mail will still be there). Do NOT restore from iCloud or iTunes (It can copy back corrupt settings)
3. Turn off system location services timezone and iAd
4. Fully discharge battery (until you get the spinning wheel and it shuts off)
5. Fully recharge battery (overnight if possible)
In my experience this improves the Standby battery drain issue significantly in most cases. It reduces drain from 2-4% or more per hr to 0.5% or less. It has worked for many, many users now. If it does not work after a few try's you may have a real battery or hardware issue and should contact Apple. Good Luck!