Belluar in his vid said all mythic nighthold is trivial for a demon hunter and didn’t bother to tell about it at all.
I had no problem with other bosses, but Botanist just kills me. If i can’t burst down arcane one quick enough tank attack oneshots me with 600k, but i managed to kill him few times
Problem starts when i get perma rooted with increasing ticks and i can’t survive for that long.
I’ve only ever soloed Telarn on my hunter, and a Cunning pet with Master’s Call made the fight faceroll easy.
It’s weird that DHs with their outrageous mobility don’t have an unsnare CD. 
Maybe the idea that the raid is uber easy is predicated on burning down everything before mechanics kick in.
Is that root ability a magic debuff ? If so then a veng DH with conflict and strife major can dispel it by casting immolation aura.
Have you tried vengeful retreat to remove the root?
it will take like five years to kill boss as veng without echoing void and i can’t kill Arcanist before he kills me as tank
doesn’t work on roots