I think it would be really wrong for anyone except the Divine to be the one to face and defeat Damian.
The conflict between them is the closest thing to the emotional heart of the story as there is. The Dragon Knight has no real emotional investment there, that ended when he/she ended Ygerna, freeing the Divine and restoring the good name to the Dragon Knights. That was the story of the last Dragon Knight.
The Divine's role is to accept responsibility for Damian, he let Damian live against Zandalor's wishes, he pushed Damian over the edge by executing Ygerna, he banished Damian into another dimension instead of killing him, and Rivellon has paid the price. The Divine has to be the protagonist for the final part of Damian's story, and he has to be the one to deal with Damian once and for all.
