Now, sure, the Dark Ranger concept is a popular demand from a portion of the playerbase. I get the desire for it.
But like has been said. It wouldn't actually fit the class. For several reasons…
Dark Rangers, by design and fantasy(and lore), aren't actual hunters.
Essentially, only resurrected Elven Rangers can become Dark Rangers. The only exception so far, was that of Nathanos, when Sylvanas herself brought him back.
Current Dark Rangers flat out refuse to give up any knowledge specific to their ways, to anyone who wasn't an Elven Ranger in the past.
Some requirements for you to be able to become a Dark Ranger:
- You have to have died followed by being resurrected. And as of now, you would have to have been a Elven Ranger in your past life.
- In order to become a Dark Ranger, you have to completely abandon any past connections and knowledge/teachings regarding the nature and the wild. Both of which are basic requirements for hunters.
Note:
Don't get me wrong here, I do believe that there's motivation for why we should have a type of Dark Ranger as a playable option available to us.
But, as far as the game is concerned, looking at design and lore, Hunters(the class), cannot be Dark Rangers. So we would have to implement them in some other way for it to actually fit.
Look past any Racial requirements tied to current Dark Rangers, and my suggestion would be to introduce the playstyle as part of the Death Knight toolkit. As it fits them much better than it does with the Hunter class. Sure, Dark Rangers, use bows, but that's about it as far as any similarities to Hunters goes.
This is also why I would say that Black Arrow as it was designed in the past(Legion version excluded), wasn't necessarily catering towards the Dark Ranger fantasy.
But more towards the fantasy of using venoms/poisons to weaken the enemy.