Hi,
I have the same problem, but it's because I already completed the end of the quest before retrieving the armor (see section "Bugs" in page Deathbrand_(Quest) at the elder scrolls wikia).
I have the wax key perk, and was able to kill Haknir without getting the armor (I didn't know at this time

)
This is clearly a bug, I would like it very much to be fixed in the next patch, because I can't get the hole armor, which seems to be really nice (I only got the helmet, other chest don't show up where they should be).
Thanks