Thank you very much, Gaze of the Adragan is the solution for the Adra Dragon. Aloth has access to this spell, I killed the dragon with a level 11 party, the only cheese I used is reload two times
I did not have scale breaker skill.
How to do it:
Eder in front, he initiates the conversation with the dragon. Rest of the party in the back.
Move Eder back (as fast as possible).
Summon something to pull the dragon to the north, does not matter very much what you summon (or pull it with Eder if you have no summons).
You can now pull the whole party (in the worst case Eder cannot be pulled) on the south side behind the dragon.
Aloth now needs to hit the dragon with Gaze of the Adragan. If he misses, well to be honest reload.
Ignore the other ememies as far as possible after Aloth hits.
If Aloth hits with Gaze of the Adragan, all party members need to attack the dragon with everything they have. If possible ignore the other enemies, or use spells that hit both the dragon and the rest.
The dragon should go down quite fast now.
Kill the rest.