The interest does not lie in the master-slave arrangement but more in the general civilization building.
The Main Problem is that you want civilizations of Dragons, going so far as having giant cities in the case of Western Dragons. Now we get to several problems at once.
Why would a Dragon live together with another? According to your fluff given sof ar they are independent beings and loners. If we go by size we have something in between a rhinoceros and an elephant in size. Not to forget that Dragons are Carnivores in general.
So we have several thousand if not ten thousands of elephant sized carnivores living in one place. That leads to massive problems.
First: Food. Imagine what each of those guys eats. Take the largest land carnivore for the moment, a lion, and imagine what a pack of 10 or 20 lions need to eat to survive. And now imagine that is what a single dragon eats multiply that by the assumed ten thousand dragons living in that city. That bumps it up to something about 200.000 lions. After looking it up a lion needs 7- 14 kg per day in MEAT to survive. Thats 2,8 Million Kg PER DAY for a city of ten thousand dragons. Now your average cow weighs in at 500kgs. Lets say for arguments sake that the whole cow is eaten. Thats 5600 Cows per day.
Now what has this to do with anything? It means your Dragons need to do Animal Husbandry to survive if they leave together in one place. Which brings us to the next question: how in gods name does a dragon achieve that?
But that aside there is stillt he problem of industrialization, a populace of Western Dragons, which value their independence and their space won't really get together to work in a Factory. Hell why would they?
But even that aside we come to yet another problem, why would dragons live together in one place at all? Your Wyverns sure, they live together in packs and hunt together and thus have already social connections. Their forming of a Civilization is unproblematic (or less problematic than the Western Ones), but your Western Dragon hunts alone. He is a loner by definition. He doesn't live in family groups, he doesn't hunt in packs. Hell he is the King of the Hill, the very, very top of the food chain. He needs no one. Hunting with another dragon means sharing meat, which is not good if you are that large.
I don't want to destroy your ideas here i just want to point out the flaws which make them less believable, my point being here is: Your Western Dragons need another race,another species, anyone else more sociable to build the Cities for them and do the Industrialization for them, because they themselves can't get together as a social group to do that.
Of course on the other hand we could go "fuck that, its fantasy, nobody cares if dragons could feasibly build a civilization or not" but that is not the point of the excercise.
Regarding Slaves, there doesn't need to be any, they could just have runt o a dragonf or protection. I imagine if the western dragon is intelligent it would be expedient to lord over a group of humans or wyverns who feed him in return for his protection against other Dragons. A kind of feudal system.
The fun thing is that the Dragons (the larger loner breeds) don't need to hold slaves of any kind or devise complex systems, they just fly in kill the leadership, declare themselves king and burn anyone opposing them, then settle in and reap the fruits of civilization.