Yeah, he has a chance of not carrying a blueprint. But more often than not he has one in his inventory. If you really need conduit blueprints, you kinda want to farm this guy. - Or wait for your luck to strike while you are main campaign farming/pushing Crucible/SR or whatever. In my opinion farming the Morgoneth dungeon is generally worth it, though. You can farm for the different Magi rings, Morgoneth Set and Conduit blueprints at the vendor.