This is exactly the same issue with my rog phone 2
If you want a better battery, i would advice to downgrade to A9 since i am currently on A9 and i see a drastic change in battery usage. Lasts easily 15+ hours of youtube and 20+ hours of Screen Off Time.
I did it but I don´t see any change or is a little better :(.
What version do you have on your asus rog phone 2?.
It's probably best to visit service centre if downgrading to A9 didn't improve anything.