I stumbled across this forum whilst searching for an issue I've been having been having with a similar (I think?) board - Gigabyte GA-J1800N-D2H I cannot get dts-hd ma audio to work. The issue is only on windows (I'm using windows 7 64bit), I can't vouch for windows 8 or 8.1, however if I boot OpenElec it works I get dts-hd MA audio using passthrough and my Denon AVR lights up with the DTS-HD MA logo.
Can you guys with this problem on your NUC systems try booting OpenElec from a USB stick and verify that the problem is resolved and can therefore only point to a driver issue?
On another note, in Windows I can see that the HECI service is not started and when I try to start it, it fails with an error.