I'd say that they are all lonesome wizards , who work on their own or they are just on 100 year quests like Gildarts did when he encountered Acnologia... I also believe Gildarts and Makarov will be on par with the weakest one and the two strongest will be above even Hades.
Altough i always hoped hiro is gonna give the dragons a human form ... It would be cool if they could turn into humans, because if they are dragons there are so many ways they could not fit into the story, with other words hiro is limited on how he can include them into the story