Oh, also another conspiratorial point of data - I got my quest item to drop for Afflic skin from the very first Eredar I killed after getting my first mythic Emerald Nightmare kill (Spider boss, if that matters). Probably a coincidence but man after all the farming I did for Demo skin, to head out after a raid and the Afflic item to drop from the very first mob I pulled in that session ...
edit/update: woo 2/2 on skulls so far. I'll probably get my first five in a row then go on a two-week dry spell of no drops :/