Having identified that a very heavily buffed Eder can actually survive the dergon's terrible rape and it's really the fucking adragans around it that cause all the trubble with the constant stun/dominate/paralyze spam, I decided to leave the dergon for the last and proceeded as follows.
I triggered the convo with Eder while everyone else was far in the back. When it was done, I immediately popped bulwark against the elements + mirror image potions on both Eder and Pallegina and started buffing Eder to fuck and back.
While Eder was getting merciless pounded, Aloth was spreading around confusions and KDs on everything he could see. Commander Boreale the rain jerk kept shooting the adragans with his stunning bow, Kana was busy summoning ogres every time he could, Durance kept buffing Eder, while Pallegina was running around murdering the adragans and high priests.
When I was done with all the minions, all of my dudes were still alive. I refreshed the potions on Eder and Pallegina and threw everything that I had against the dergon to surround it with as loose a formation as possible to make it switch targets constantly. So it was surrounded by Eder, Pallegina, Cpt Diomedes the lion, 2 summoned ogres and 2 summoned wurms, while Aloth+Eder kept knocking it down.
When it was down to 2 blips of health I realised I still have Adragan's Gaze, so I cast that. First failed, second hit. Then the dergon got hit by two ogre clubs for 120 and 140 damage and keeled over. I still had so many KD/stun sources left that I doubt I even needed to petrify it, but it was just faster that way. Only Durance and Boreale got KO'd in the fight because they were too close to a stray wing flap.
GG WP
LIINK