The baz is the best way to farm those. But if you want to waste your time then yes, the Neriak 4th gate HA have a slightly better drop rate than regular Neriak. That means you might see 1 in 10,000 mobs in the HA and 1 in 100,000 mobs in regular zone. And this was increased back in 2019 after much whining. This is why they are so expensive even when you do see one in the baz for sale. Only the Beryl ornaments are more rare, but the Beryl are TLC And Wither and Decay are slightly better than Dark Elf. Getting full sets for my chain, cloth and leather took forever (years) and were a huge let down in looks. There are others that are way better.
They drop just gotta be a certain level range which is stupid. I wanted bixie and wait for people to sell in the baz.