Proud owner of LG G4 but...
Was using Meizu M2 note where I could easy achieve 6 hours on screen time, and decided i need more power so i bought lg.
Updated to marshmallow (v20d) and my battery was really bad. Then i did a reset to factory settings thinking it will be better, but the battery is the same, max.2.5 hours on screen time and the phone couldn't last more than 12 hours.
Then i turned off activity logs, uninstalled lg health, disabled search, voice and etc.history in google app, disabled google apps which i don't use (music, news, games, movies), deleted facebook app (leaving fb messenger), gps using only networks and voila!
I am on 60% battery left with 2 hours on screen time and 9h using the phone since i charged the phone

The phone is great and i like lg software but it's the apps which are making wakelocks and battery drain. I really think doze is not helping with this phone because i was using lg g3 earlier and the battery life was the same without doze.