So basically you whittle him down over time by keeping him frozen or stunned? Ok I will try that this coming weekend (weekend cause I can see through the 90 min attempt I made yesterday that I will need to block out a couple of hours for this).
Someone else suggested not trying to take out his initial summons in any hurry but to keep them occupied with my own summons while I alternately heal astarte, stun/freeze the dragon and whittle away at his health.
I am going to go out and steal every painting, loot every house, buy every scroll, potion, power/attribute I can before I head back into this fight and I will scroll this sob to death if I have to!!!!