What level do I have to be to kill Hinterlands/Storm coast dragon?

Solution 1:

You could do it at level 11 - but it's really tough. You'll need a good composition, armor with high resistances and lots of potions to help you. I did it at level 16 without much preparation and it was a breeze (on normal). Just make sure to dodge the fire blasts from the sky - those can really hurt, especially at level 11!

The Storm Coasts dragon flies off to a place which cannot be reached until much later in the game, after doing a quest. Mouse-over the block below to find out more (warning: SPOILER ALERT).

The sidequest is called Red Water, which opens up Dragon Island in the Storm Coasts.

Once you can reach it, I think it's level 19, so no - no chance of doing that with a level 11 party.