Issue: The Hunter chest armor from Ghosts of the Deep does not render while on the HELM. It doesn't render in the game world or menus. It returns to normal when leaving the HELM.
How to replicate: Wear the "Vest of the Taken King" armor piece (any shader) or transmog another armor piece with the "Vest of the Taken King" while either being loaded into the HELM or loading into the HELM.
Prevalence: I've seen this both in my own game and on streams of others' games. Other Hunter players report the same bug.