I don't mess with my phone all that much and use a limited amount of apps. Both my boyfriend and I have the S6 and with the last Android update have noticed severe battery sucking going on. I disabled the Faccbook app and cleaned up my screens and removed apps I wasn't using and put Doze on and use power saver, and it's better, but generally I'm down in the teens percentage wise by the afternoon. Since my boyfriend is experiencing the same issues that started at the same time I'm guessing it's the update.
Current version:
G920PVPS4CP13
Android 6.0.1
Security patch 9/1/2016
Current version:
G920PVPS4CP13
Android 6.0.1
Security patch 9/1/2016