Kevin, I can prove this is an issue with the Intel drivers...
If you will please.
1. Fresh install of Windows 8 x64 on Asus Z87Pro Motherboard, 4770k Processor, 16 Gigs of DDR3 2133 GSkill RAM and a Samsung 27" and a BestBuy Insignia 39" screen.
2. No drivers loaded.
3. Set monitor sleep time to 1 minute
4. Monitors DO sleep fine. This is using the "Microsoft Basic Display Driver"
5. Next install the Intel 3165 drivers, once again no other drivers loaded for motherboard.
6. Monitors do NOT sleep.
7. Re-image back to normal set up.
Links to DX Diag reports before and after...
Before ANY drivers here: https://dl.dropboxusercontent.com/u/31360541/INtel/DxDiag%20-%20No%20Drivers.txt
After JUST the display driver here: https://dl.dropboxusercontent.com/u/31360541/INtel/DxDiag%20-%20No%20Drivers.txt
I have no doubt that its the drivers. Let me know if there is anything else you can test. I have the liberty of dumping my OS at any time.
Im about to load up an Ubuntu stable release and see how that goes... Will let you know shortly.