Damn, he's the shove boss. Didn't realize it as he went down first in both of my playthroughs( point blank range cleric with inflict wounds + rest of party assisting from stairs).
But ngl if someone at Larian wants some fights to revolve around shove make it a dragon fight.
If you get pushed by his wings and there's a brick wall behind it you are also stunned for 1 turn and go THROUGH the brick wall which then collapse dealing 1d2 per brick. There's at least 60 bricks.