Even though my UI shows ‘Heroic’ and ‘25 man’, I noticed today that I had to set the raid difficulty to Normal and then back to Heroic for the skull to appear on the enterance.
I only discovered this after probably 50 ICC runs not expecting this, so I am rather tilted as I’m not sure how many of these runs/weeks have been a waste of time. Found out when I went to buy transmog and my vanquisher tokens were all normal tokens.