I started a new game when 2.0.19 came out. (I restart to often, but I am still having fun, so it is okay :->)
In my newest game (the one started post-2.0.19) my mage is currently level 35, I have spent the game (thus far) farming Realm depths 2,3 and 4 (mostly 2,3 and a bit of 4).
I currently have found 8 Legendary crafting materials. (I haven’t seen a Nether Orb yet, but I have EIGHT legendary crafting materials.) Also, as a point of comparison, I have found 8 Minor Sigils (and no Major Sigils).
This is obviously a small sample size, and so it could be that I got crazy-lucky farming low-depth realms early in the game. On the other hand, it could be a sign that something is subtly wrong with the loot distribution table in 2.0.19.