He already asked Patriarch to open a passage to the Hall of Echoes, but was refused. As the last dragon knight, the player character was the only hope he had of implementing his plan to resurrect Ygerna.
From what I understood, he had no plan to ressurect Ygerna (or at least not now, and the dragon knight was not in it). And once the Patriarch opened the passage, Damian had no use for the Dragon Knight anymore.
For principles I am against putting myself too much handicap (but that's just me), and having points I don't spend is an heresy (in my opinion, but again it's just me).
