Did you try to set manually cache clock to 3000 or higher ? I see 1500MHz in CPU-Z/AIDA but on my board it was actually read bug and whatever I set, it was 1500 in system ( even though performance was fine ). When I changed to newer BIOS then software was reading it good but performance has dropped
In general I like design of this memory. Too large etc but on this platform it's not an issue and what's more important , it looks good

The same as Predators on DDR3 but finally black PCB and black/gray color scheme.
This motherboard has profiles for Hynix and Micron memory ( I believe there are Hynix chips but I can be wrong ). I would try the one with tighter timings and compare performance. For some reason on my MSI all profiles with more relaxed timings didn't work at all.
DDR4 is not really slower the same as DDR3 wasn't slower than DDR2. The main issue in all cases are early memory controllers or other things that block max bandwidth. On X99 main issue seems limited cache clock. After raising this clock you may achieve much higher memory bandwidth without even touching any memory settings ( and I mean something like 5-10GB/s better results ).
When DDR3 was released then we had X48 and X58 platforms. X48 was slow as C2D were not really designed for DDR3 but X58 was great. My 1st DDR3 kit was 1600 7-7-7 1.65V and it was not long after DDR3 premiere.