After the upgrade to iOS 6.1.3, I experienced massive degradation on the battery performance; to a point where the phone was unusable. I’ve tried many things, from turning off gps locations, turning off wifi, setting it in airplane mode, removing access to calendars, turning off iCloud related functionality, and closing out all the apps.
I think I found a decent solution. It seems that iOS 6.1.3 somehow breaks the push and exchange process, by turning off push on exchange accounts, my phone seems to work normally again. the only drawback is now when getting email, you have to load up mail for it to go fetch.