Personally I doubt it. I think they are two different things entirely, and work differently, their powers are different in nature, Banshees Including Sylvanas, seem to have much more Shadow related powers, as opposed to Unholy Blood and Frost. Now those are game mechanics, but it does very much seem like a Death Knight’s Spirit is bound to its body, unlike that of a Banshee. Now the interesting question is, Is it only Sylvanas who can do her Banshee thing still? We never see any other Dark Ranger able to do this, after possessing their own body, and if we’re being technical about it, what we see in the BfA trailer is not a Banshee power. Banshee’s possess their bodies (or those of others) Sylvanas outright ditches hers to use her Scream ability. There is no body for her to possess, even hers…she just reforms.
We never see any other Dark Ranger do that.
The other question is, if she can do that at will, then why make herself vulnerable at all? If she can just zip around the battlefield screaming and killing people, then…why doesn’t she? I mean that would be a hell of a battle winner?
From that we can hypothesise that she can’t do it for long, it takes effort, and is a last resort. I mean why not do it in her fight with Genn? Why not in her fight with Malfurion? Perhaps other Banshee’s simply are not powerful to do it once they become a Dark Ranger, or else why aren’t they all zipping around killing with ease?
A Dark Ranger is essentially Undead, so one turned into a Death Knight, assuming it were even possible, basically would be an Undead Death Knight, not a Death Knight/Dark Ranger crossbreed. It might still look Elven, but it is essentially an Undead Death Knight.
Nathanos is a special case (In more ways than one 
). There isn’t really a name for what he is, he’s not a Death Knight, and he’s not a Dark Ranger.
We know he was human, and male, therefore cannot be a Banshee. In any case we know he didn’t re inhabit his body, he never left it, it was the standard male Forsaken. That’s all he was, a Forsaken Hunter. As such, he does not class as a Dark Ranger. He also is not a Death Knight, he is no longer in his own body. We don’t even know if Sylvanas’ Val’kyr have the Power to create new Death Knights, We know Bolvar and the Deathlord can.
I’m sure there is a name from Fantasy mythos for what he is, its on the tip of my tongue, Basically a soul in a dead body that is transferred to another dead body…though not by their own ability… Anyway, he is neither a Dark Ranger or a Death Knight, he’s the only one of whatever he is, and apparently his creation was extremely taxing on the Val’kyr.
That is a definite reference to the Goth band Siouxsie and the Banshees, and not the only one, Blizz obviously have one of their fans writing NPC’s and Quests, a couple of the bands songs are quest titles, ‘Face to Face’ and of course the finale of the Silverpine quests “Cities in Dust”.
Good band to be honest…
