Level 19 at the moment and some of the dragons still kicking my ass.
I've killed 4. Tried one earlier and every time you get it's health down a little it gets it's guard all the way up. Tbh, it would just be boring to slog through so I left it.
Btw, I have to say that the game post-campaign is very disappointing. Skyhold for some reason becomes really bugged, with people disappearing and stuff not loading. Also, none of your companions will talk to you and all of their quests disappear.