I've been having the exact same problem with my ASUS ROG Strix G15 (G512LW). It seems to be pretty much the same spec as your system, I'm also running BIOS v314
Have you also noticed that the fans seems to spin non-stop once the display turns off? (better than the previous boil the CPU scenario, but still annoying...)
I seem to have narrowed it down to sleep mode too, as when I turn off the display sleep, it seems to go away.
I did find turning off Connected Standby helped, but you need to add PlatformAoAcOverride with value 0 to the registry location HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Power. This is because even with turning off the display sleep or automatic sleep, Connected Standby still puts the system into a low state of power, but ultimately it didn't fix it completely. You may want to run powercfg /a in command prompt to check if S3 is available AT ALL though.
I'm currently trying to figure out if one of the Services you can disable in msconfig is the issue. So far it's been fairly reliable, but I do find that I need to soak test for about 2-3 days to really see if it's worked or not.