I’ve just completed this quest with my friend on our alts. I have Durnand Priory Asura, she has Order of Whisper one. We both were on story step when we both needed to defend LA. We completed the quest and then quest completed for her without question. (like: there were no window asking if he choose to accept the progress) And as I know, her diary entry about Battle for Claw Island was bugged afterwards – cut in the middle of sentence.