There is a ton of lore present about the Dragon Knights in Divinity II: Ego Draconis and its extension story, Flames of Vengeance. It's also the last game in the timeline, the Original Sin game taking place several centuries before. That is likely the reason so little mention of the Dragon Knights is in the game, because of its place in the timeline.
Note that, although the Dragon Emperor was considered a Dragon Knight, he is the offspring of a human and a dragon, and isn't necessarily a Dragon Knight created by Maxos as by tradition. So, while Dragon Knights may not be mentioned, Half-Dragons would likely also make an appearance, since we have all of the original Divinity Races in the roster (we only got Humans and Imps rendered in Original Sin).
