I was under the impression that these cults, such as the Twilight's Hammer, the Damned, the Burning Blade, are all but destroyed in each successive assault on the enemy stronghold, save for disparate cells outside their home range. It makes me wonder if we'll be seeing any insurgent forces into the Dark Portal such as the Burning Blade!
It just feels like they were a flavor of the year used to attract people to the game and now they're just another rank and file. I love Death Knights a lot but since each and everyone of the DK players are partly members of the Knights of the Ebon Blade in Acherus, there certainly seems to be a lot of stagnation on their story at the moment. I would have loved to see them take New Avalon as their home city where they could at least take the part as the dark half of the "emergency force".
By "emergency force" I mean an organisation similar to the Argent Crusade stationed not too far away. This is at least how I think things should be. If anything I'd like to see a dual-faction guild set up called <Knights of the Ebon Blade> or <Ebon Crusade> stationed in New Avalon as neutral ground. To me, this is how it should be anyway since the Lich King is indeed safely entombed once more in ice.
In my opinion at least, even though the lore is contradictory, these Death Knights aren't really tied to their home faction beyond their species and prior affiliation. Even Thaurissan and Koltira are still friends despite their allegiance to Wrynn and Lorthemar respectively. I see the Death Knights as I see Paladins. More of a tertiary faction in their own right, neutral, arbitrary and a safeguard against the coming Burning Legion.