He actually does have unique dialogue if you save him, but not much. Trying to talk with him after saving him will have him say, “I don’t want to talk about it,” and immediately end conversation.

Additionally, Tamriel Rebuilt makes him the court mage at Old Ebonheart and adds a quest about selecting a replacement after he dies. Or, if you managed to save him, you can find him in Old Ebonheart for a reward.