I figured out how to make the DZ87KLT-75K fully compatible with Haswell refresh, in this post i confirm with a Core i7-4790K Devil's Canyon runs perfectly on the motherboard, short story is i had an i7-4770K initialy and happend to be in a position that allowed me access to the i7-4790K brand new boxed since i got it to work its now my main CPU in the DZ87KLT-75K
Before the steps as we all know the Haswell refresh CPUs are detected correctly in any 8series board by Intel, so what causes them not to function correctly is the Intel Management Engine (Intel ME), intel decided not to update the ME while updating BIOS, so the trick is just to update the Intel ME to aversion that come around same time as the Haswell refresh.
Steps
Assuming you have downloaded all the correct required files
1. I installed Core i7-4790K
2. Switched on PC booted into windows
3. I then followed steps to install
Intel ME 9.0 Consumer 1.5MB Firmware v9.0.31.1487
using this tool
Intel FWUpdate Tool for ME 9.0 Firmware v9.0.22.1467
I used the win tool in windows not dos
Everything went well shut down the PC then powered on again and all was well, restarted several times, even tinkerd with memory settings saved several times, run a stability test for 8 hour and all was ok
Intel ME files are found on this website along with all the necessary tools and instructions
http://www.win-raid.com/t596f39-Intel-Management-Engine-Drivers-Firmware-amp-System-Tools.html