Had the 8-core Haswell-E, stepped down to a Skylake 6700K for a while, and now on 6800K and a new X99 board (ASUS X99A-II) and 4x16GB DDR4-2400 DIMMs.
The issue with the Haswell-E actually turned out to be the fact that I was populating all 8 DIMM slots with DDR4-2400 RAM and trying to run it at that frequency. The memory controller is apparently only rated for DDR4-1866 on all 8 DIMMs. Issues went away when I ran the RAM at DDR4-2133, but I felt like going to Skylake at the time anyway.
I actually found a really good read about this particular issue by someone from either Asus or a memory representative just recently. I had always assumed two matching dual channel kits would be just as good as a quad channel kit, but this stated that is not the case at all. So I can see why you had some issues trying to run 8 sticks since there are no such "sets" available for sale. Let me see if I can dig up a link.
http://rog.asus.com/forum/showthrea...e-memory-kits!-The-meat-and-potatoes-overview