Like the other epic mobs, dragons require huge groups of players in order to be defeated. The usual technique against them is to get someone to lure them and make them run around, while everyone else attacks.
Dragons have 2 powers, one "flame spell" (element varies between realms) that activates if he gets close to his target, damaging anything in front of it. They also have a stomp strike, that has a very similar effect to Sultar's Terror. When the dragon flies in the air and hovers for a second, everyone will run for it as he is about to use this technique.
Though they share the same model, there are aesthetic differences between the three of them.