I was able to get my Crux after following the formula of having the glowhoo equipped and not doing any other raid before Crota on hard. I already had my Eidilon Ally fully upgraded waiting on the crux. I'm currently working with my clan members to get whoever else the crux too. It took a good while and I don't raid as much as I'd like to but it popped up for me. If possible try to be the sword runner as well. I say to my collectors don't give up on it. My next quest is a mythoclast.