I came to Jaws of Hakkon during a playthrough that had not finished the game and had been fighting in Emprise. Cory is still very much alive and the Inquisitor was Level 22 entering the Frostback Basin.
I used my Rift Mage Inquisitor, along with mages Solas & Dorian, with Blackwall as the tank for both Gurd and the dragon. Everyone had Guard on their gear and the mages had fire staffs. Solas and the Inquisitor had Pull of The Abyss. The party had confusion cold & spirit grenades along with two Jars of Bees.
For me Gurd was a much tougher fight on Nightmare, but I won on the third attempt. The Inquisitor did use Mark of the Rift at the second spawning of adds and the three mages stayed together for Barrier near the fire. There was minimal running around, but I did refill my potions during the final fight.
Before engaging the dragon I went and killed in the zone to replenish my focus. That proved to be unnecessary. I kept the same armor and added one more staff with a Master Dragon Rune. The mage staffs had masterworks that added offense.
The fight was unexpectedly easy for me. Before entering the battleground there were some potential adds close and we killed them. Then we climbed to the battleground and used normal dragon fighting techniques. I continues attacking with my staff and Energy Barrage even as he flew away. I never had adds and I never had to use any focus abilities, not did I use more than one cold resistance potion.