I feel you on the story missions if you can call them that.. NO STORY AT ALL! Just a couple of lines of dialogue and basically go kill everything and not even a single cut-scene or character development or anything just extremely poor. That said, the strikes were good and I enjoyed Undying Mind also. The nightfall unlocks you just need to complete a bunch of Eris missions to get to it. Bungie has legitimately shown they in no way know how to cultivate characters, story or interesting plot lines.