If your Usage time and Standby time are the same even when your phone is in sleep mode, there is something wrong. Most likely there appears to be a rogue app running in the background.
Few things you may want to check:
1. Mail. Sometimes after every update, your mail server can hang and continue to check the server. Deleting your mail account, rebooting and recreating the mail account seems fix the issue for some users.
2. Double click home button to bring up recently used app trays, hold the app for 3 seconds until a red circle with "-" appears and tap on it on all of your apps. This will close the app. If you have a systems moniter app, you should be able to tell what apps is running and what app isn't. It is a useful tool. I use this tool to free up memory spaces and check what apps are running.
In addition to number 2. Most app that supports multitasking usually should go into a frozen state. Meaning the app will freeze and shouldn't be running in the background. Only apps that would continue to run in the background is your navigation app and if you are actually using it.
3. Location service. If see an arrow next to the battery meter, then your location service is active and is running in the background. Check to see what app is still on. I know for the fact that if you set up a location reminder, the arrow will continue to stay there until you reach your location.
Also if you aren't using location service, best to keep this off.
If none the above fixes the issue then here are few suggestions that may work:
1. Settings > General > Reset (scroll all the way down) > Reset all Settings. This will reset your settings, it will not erase any contents. Some people find that this helped them fix the issue with the same usage and standby time.
2. Hold the home button and the power button for 10-15 seconds until apple logo appears (ignore red slider), this is a hard reset.
3. If #1 and #2 didn't do the trick then restoring your phone is the next option. Try set up as new phone and see if that helps.