You should check Event Viewer at the time for specific information! Since Windows will log everything (both hardware and software events).
Black screen of death happened to me once. But it happened after I restarted from bios instead.
I messed up my Windows so I need to reinstall it.
All I did was to make BIOS to boot from USB in Secure Mode and enable Fast boot(Quiet boot).
There, everything happened. Backlight didn't work(still saw black screen if I pointed a light source at the screen). Keyboard stopped working(capslock stay on)
My final decision was RMA.
They said the mainboard was dead from unknown cause. They had it replaced in 20 working-hours(nearly two days).
Now everything is back to normal.
I assume your case is windows issue due to "Sleep" not harddisk, in case Harddisk turn off timer, "never" means the Windows will keep your harddisk running forever as long as Windows stay on. If your log shows hardware issue, you should contact the nearest Asus Service Center.
FYI, Windows sucks at this, Sleep timer starts to count down from the last interaction from mouse or keyboard, so if you are playing game with controller, or watching movies, make sure you turn off sleep timer or enable "Prevent sleep mode" thing in settings.