I originally posted this on the console bug reporting forum, but got no response.
I have completed several tier 30+ NM dungeons with no distilled fear dropping.
My consumables tab is full but i already have 2 distilled fears so it should still stack if they do drop.
Is there only a chance to drop or is it bugged?
It is only a chance to drop - good luck 
They START dropping at NM30. Higher the NM dungeon the higher the drop rate. Over 60 it’s almost 100%. They are still dropping. P.S. - clean out your consumables tab ;0
Ok, thanks for the info.
I can definitely tell you, over 60, it’s not 100%. I’ve been doing nothing but Nightmare dungeons, all Level 90+, and it’s more like 60-75% which drop the Distilled Fear.
I think the 90-100 range is bugged loot. I always get sacred items in the main reward window. I did a bunch of 70s and got the fear each time. Maybe try to stick in the 65-80 range, lol
https://drive.google.com/file/d/1x96fQIqoPyIlbH22eOmldH-x6WlfBW5g/view