Fury616
www.illdust.com
At what level could yall kill dragons
When you get to Skyhold.
Just make sure Viv is upgraded in Knight Enchanter(KE) and Spirit speciality and the "Fade" ability from the Winter speciality. If she isn't, then respec her to be so you can easily kill dragons.
If you're a mage, then be a KE. Either you or Viv can solo dragons or anything else in the game on any difficulty.