Confirmed, you NEED to have completed the scryer in order to complete the final part of the quest. You may be able to use someone else's scryer in the final fight but each person/pally must have progressed to that part of the quest. Recently a pristine black dropped during a Scholomance run, three people rolled Need for it (me, my guildmaster who is also a pally and a warlock) and of all thing the warlock won. Needless to say he got blasted by me and my guildmaster since that was the only REAL reason we were running the instance. :) Well guildmaster ended up getting the diamond traded to him. He ported out, got his scryer made, then came back and we finished the inst run down to where Rattlegore was. The fight went better then I expected (although my guildmaster had NO idea about the Judging of Seals for the AOE stuns against the spirits), only two deaths and one because he was a 55 level mage. Guildmaster got his mount, I didn't. Ah well, back to pharming for the diamond, I guess.