The issue has not comeback, battery is doing very well. It looks like this issue is related to corrupt exchange accounts.
I recommend to anyone experiencing this issue to delete the exchange accounts they have 1 at a time and add them back with a different account description. If the battery starts acting better, then dont delete any other exchange accounts you may have. If the problem still exist repeat with the next exchange account you have, assuming you have multiple exchange accounts.
If the problem still exist, restore with a fresh iOS install and configure iPhone as new (do not restore from backup, yeah I know...it sucks).
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yes, it does mean your iPhone is not going into standby.
Do you have a exchange account? If so delete the account and add it back. Others, along with me have found a corrupt exchange account to be the culprit.