Currently the only two places to kill black dragons in the game are in the Barbarian Dungeon and in KBD's lair in the Rimmington Dungeon. In the Barbarain Dungeon, there are only two tucked away in the far corner which is incredibly tedious to get to, on top of generally being an incredibly inefficient spot due to the low amount of black dragons. In the Rimmington Dungeon, you have a wonderful amount of black dragons to kill in a multi-combat area that would be incredibly efficient for multiple players, which is more or less ruined by the presence of KBD due to his INCREDIBLY large aggro-range (he can basically lock onto you from halfway across the room). Basically, both of these spots aren't that great at the moment. I would like to see some possible changes to make these spots better.
Firstly, I think we should consider moving KBD from his current spot in the Rimmington dungeon. His lair is so massive and yet he makes using it for any reason that's not to kill KBD nearly impossible. You can't efficiently kill black dragons there without constantly being harassed by him. If possible, maybe doing something like in the Kalphite Lair where KQ's lair is seperated from the rest of the dungeon by a hole in the ground leading to another room would be nice, allowing us to stick the entrance to his lair in the same spot as it originally was to avoid confusion. Not sure how possible something like that is, but it'd be nice. KBD's lair could therefore be a smaller room in a multi-combat zone still connected to the Rimmington dungeon, and he could possibly still be aided by a couple black dragons. The lair on the other hand could now be used to kill black dragons as well as possibly housing a second mob inside of it to give the dungeon a little more diversity (hint: Green dragons).
As for the Barbarian dungeon location, all I'd like to see is simply making the Agility shortcut leading to the dungeon's rear ladder in Catherby usable. Makes getting to this spot (and the rear of the dungeon) so much freaking easier.