Hello 
For the last 3 days I was trying to farm the Korvan Helm. I need it to craft the Occulant Shield.
The area I do the farming in is Cairan Docks. I clear it, reset and start over. I did it at least 50 times over the last 3 days. While I was able to get multiple Korvan Casque and Korvan Gaze helmets, the actual Korvan Helm just doesn’t show up and it is starting to get frustrating. I’m wondering: Did that helmet ever drop for you within the last few patches? Does it actually drop?
RNG
got one yday clearing it for the quest
the issue you’re probably having is this
*low density of actual mobs dropping it since bunch of spawns are the white kind
then the item ofc shares drop slot with the 2 other, and the base drop chance to get a helm is already on the lower side (relatively normal chamption mob drop%)
heroes bump that up to 5%
but they are also not really that frequent in spawn i feel
Thank you for confirming that it actually can drop! 
So, I have to keep on grinding then.
try ToH, not 100% if confirmation bias or actual mechanically accurate, but i feel like i get more korvan armour drops in ToH runs than in Cairan docks, largely because it seems like outside ToH there is more white mob spawns, but also more wraith heroes than armour heroes (no clue if they are replacing eachother)