The Vaykor Hek already has an innate syndicate proc as well as better stats than the Hek, so Scattered Justice would be complete overkill.
Gleaming Blight does fit in the Rakta Dark Dagger, probably because it doesn't have an innate syndicate proc. Note that stealth and Gleaming Blight don't work well together as the syndicate proc makes you lose your stealth bonus if it hits any bad guys.