Diamond Yogg-Saron after event?

I’ve been revisiting mercenaries after some time, and I cannot see where I am in the Yogg-Saron event chain that expired long ago. I wasn’t able to finish it to get the diamond frame, but was attempting the achievement merely by doing the quest to see if I can earn it that way. No luck, but do we need to ‘redo’ some of the tasks from before to find out where in the chain we are to work up to the diamond frame rewarded task? or do we need an old-god style event to trigger to get those frames as rewards? I know some are obtained through packs, but I still see you need the achievement for old Yogg himself. Thanks for any advice/help!