Yesterday Blizzard announced that in the upcoming Patch 9.0.5, Valor points will make a return in Mythic Keystone dungeons and allow you to upgrade Mythic Keystone gear.
I have mixed feelings about this.
The one really good thing about Mythic Keystones is that there is a constant push to do higher and higher Keystones. Better gear from the dungeons, better gear from the Vault, a higher Raider.io score so you will be accepted into better groups, everything pushes you to keep climbing.
That is actually pretty rare historically. Whenever quality of reward scales with difficulty in repeatable content, players target the highest difficulty they can do. However, whenever quantity of reward scales with difficulty in repeatable content, players instead go after the easiest content they can do quickly, optimizing for reward per unit time. And Valor is pure quantity of reward.
We saw this every time Valor was introduced previously, from Mechanar onwards. We see it in Diablo III, where players farm the easiest Torment they can do in 5 minutes instead of the difficult ones.
The worst thing that can happen to Mythic Keystone dungeons is if players stop pushing high keys, and start running low keys incessantly just to get Valor quickly.
I think the Torghast model of rewarding Soul Ash might be a good fit. Let's say you get a 100 Valor per level of Mythic Keystone. So if you do a +2, you get 200 Valor, a +6 is 600 Valor, and so on. If you did a low level and then a high level, you only get the difference. So you only need to do the high level. You could do it for each dungeon, like Torghast does for each wing, encouraging people to get a spread of high keys.
I guess we'll see what model Blizzard goes with. But from my point of view, Valor points are dangerous, encouraging a spammy, non-challenging playstyle which brings out the worst in the playerbase.