Problem solved, it turns out that the BIOS has gone bananas for no apparent reason. No direct relation to BIOS changes or any hardware changes when the problem first occured, it just randomly snapped. I was led to this after I changed ssd and ram, after which the problem remained. Then I just forced reflashed the BIOS and now it is as good as new.
I've had this problem ever since I upgraded to Windows 10 (around January). I believe the cause of the problem is the driver for NVIDIA conflicting with Windows 10. Actually tried the driver update for NVIDIA from Windows Update before and my sleep somehow worked (but a little clunky), however, using the drivers from NVIDIA prevents me from going to sleep and results in BSOD. You just have to live with it until MS or NVIDIA fixes this bug. Give us some update if ASUS fixes this. Might only be a problem for specific video card models.
EDIT: We actually posted around the same time. So the BIOS is the root cause? Flashing removes the BSOD?
Yes it was the BIOS after all. No idea why. I was led to the conclusion that it was not a software problem after trying A LOT of thing, the last of which being replacing the laptop's SSD with its original one which I have kept without formatting. In the original SSD I had windows 8.1 in a working state, as I had replaced the SSD before upgrading to windows 10. Seeing that with the original SSD I had the exact same problem determined that software/drivers/whatever was not the case.
BTW this is the first time that I am hearing about the nvidia drivers problem in windows 10. I am a heavy cuda user and I never had any problem using the very last geforce drivers, directly from the nvidia site.
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