If you killed the Hinterlands dragon and you weren't awfully over leveled for it, you should be able to kill of them as long as you are an appropriate level for each encounter. That dragon moves around much more than any other (with the platform things) and the adds can be a pain.
As people mentioned, besides the basic mechanics that apply to all dragons (tail lash, wing flap, claw, breath, fire/cold/electric balls) the only special behaviors to watch are:
- The lightning debuff from lightning dragons. You can dispel it if you're quick, or simply make sure none of your characters are standing inside another character's circle (it's fine if the circle overlap slightly, as long as nobody stands on someone else's circle).
- Lightning dragons on water. They sometimes electrify the water, so don't stand in it.
- The adds. Kill them fast.
AS long as you're not under leveled you'll probably be fine, since you already killed 3 of them.