As only seasonal dungeons are available on Mythic difficulty, you have until March 4th - The release of Season 2 of The War Within, to get credit on the Season 1 dungeons for the achievements above:
Continue reading »
The War Within Season 2 starts on March 4th, and with it, new dungeons will be available to get credit for the Algari Dungeon series of achievements - Which requires you to clear all Khaz Algar dungeons on Mythic difficulty.