Realized I was close to having a 'mythic complete' set for Outlaws of Thunder Junction and decided to go for it so I could get the "Completionist" title reward from the Achievements.

With the new duplicate protection for different sets, the UI says I have all 4 copies of Terror of the Peaks since I have a total of 4 across the M21 and OTJ versions. The Set Completion tracker also has a big glowing "Mythic Complete" outline, however the achievement has not triggered and registered that I have successfully completed a set.

Thanks.