Mythic+ dungeons aren't for everyone; especially high-end dungeons, because they are reserved for the best-of-the-gray players, who will be forever etched on the walls of Blizzard Entertainment's hall of fame. However, not all players were upfront in their quest, and the developers were encouraged to make mid-season adjustments to the high-end Mythic+ rating, promising further improvements in future seasons.
On January 25, one of the World of Warcraft developers said maintenance next week would make changes to the Mythic+ rating, and completing a level 21 Mythic+ dungeon or higher and not timing the key will only give you rating as if you completed a 20 Mythic+ dungeon.
The main purpose of this change is to discourage players from using the system in order to earn a seasonal title, such as the Thundering Hero title. Some players may fall below that 2400 rating, requiring them to earn the rating once more.
"With this change, some players who are just barely at 2400 rating, some of that rating coming from untimed 21+ keys, may fall below 2400 and need to re-earn that Rating in order to continue upgrading new items to Rank 13," Blizzard said.
One of the team's developers said the team is contemplating changing the scoring system as a whole. Right now, a major shift is not feasible due to the large majority of Mythic+ players losing their points and falling below a significant threshold.