With this dragon at this stage of the game, LOTS of summons (with high hp, like Bears) to keep him distracted help immensely. Looks like you'll be arrowing it to death. Keep your group around the dragon -- wolf pack tactics. One wing buffet can send 3 or 4 of you flying, and this dragon likes to wing buffet. Attack from all sides, hit him with arrows while summons distract him, and use healing potions (and speed potions). This dragon has enough room in his area for you to do the "can't catch me" bit as well. It is easy to dupe him into chasing one or two folks around the room while others hit with arrows.
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