Since dragon's don't actually exist, they can be whatever you want...
Yes, but they have to feel right. Why should a thing like that team up? Against a bigger, nastier predator? but you've been writing your character to the top of the food chain, what ignominy to downgrade him to a jackal to some tiger. A prey animal so big that a solitary hunter can't take it down? Better, but you don't need a number of the standard draconian accoutrements; you don't even need the wings (there may be those among you pointing out that Chinese dragons do not have wings – they still fly. Presumably lighter than air.). And the flight, and the fire have become what distinguishes a true dragon from a mere ground-crawling wurm. Perhaps they specialise in smaller prey, and the weaponry and armour doesn't detract when they get together to attack the huger. Most likely, though is persecution by a social species of smaller predators, and humans stand in very well for these; developing technology, merciless, self justified…
You are going to tell me that, since this is fantasy, everything is created by an ineffable creator (the author, unless you are particularly into effing), and that evolutionary logic need lay no restrictions on their practicality. But the great creators lubricate the path to believability with feel right details Smaug is hopelessly unaerodynamic, but you never sense this while reading. Holly Lisle's Minerva dragon, though, is a clown, used on Earth to generate a sense of the ridiculousness of the situation, weakening the male lead's grip on sanity, but not a character
There's always the possibility, since we have no humans for reference, that these dragons are eighteen inches long in an ecology to scale. You don't have to tell your readers this, but it simplifies the physics and means you can get by without wings three times the length of the body, for example. And possibly teaming up becomes more profitable, and even tool use has its advantages (I'm trying to work out reasons that dragons would develop a society).
People love dragons. Even mine, who are about as down to earth, uninfected by cosmic sagacity as you can imagine. But suspension of disbelief for a fire-breathing, armoured flying reptile (all necessary characteristics for earning the name, in my opinion) is not easy to come by. So work out in your own mind what needs to be, and what that means for the conventional monster. Don't tell your readers anything they don't need to know, but you having a clear, integrated image will come across.
