Since 8.3, portions of the Moonpriest’s Vestments no longer display, specifically the belt and one half of the feather trimming on the hip. This occurs on multiple computers, and is persistent through repairs and relogs. Not sure if there are other sets affected by this yet.
On further inspection, this appears to only affect draenei and lightforged draenei versions of this armor.
Added: This also can be seen on my character page.