The dragons are meant to be defensive only for the AI, so if you are not right on top of the AI you shouldn't have to deal with them until much later when you are extremely powerful. At a certain point, by leveling up your cities and doing other activities, even the dragons will be like paper before your forces. You shouldn't have to interact with them unless you are very close to an AI homeworld, unless there is a new bug I'm not aware of (which is possible).