Tried everything, the only way to make sleep work is to enable intel graphics, and then sleep works. As mentioned earlier in the post, the disadvantage is that you will not see the boot screen or clover startup screens and will see life when the ElCapitan logon screen appears.
For those who can don't want to attach another monitor, a tip. Please use the unused hdmi / DVI / display port on your primary monitor to connect the onboard display output to the same monitor. Then, by toggling inputs on your primary monitor to the onboard output, you will be back in business on being able to see startup screens of the desktop and clover.
Something i have not been able to resolve, extremely sluggish mouse after waking up from sleep, but does work.
For z77 users, who have a HD4000 graphics and second monitor connected thru the onboard HDMI, please set screen resolution to 1920x1080 in the GUI section to avoid a garbled screen on the login screen. Otherwise, it will show up as 3 or 4 screens on the monitor.