Mythic key runs have literally nothing to do with this game.
You have a timer, so that right away makes it the most important thing; rush through trash and aoe them down as fast as possible, pay attention to affixes...
Dungeons in wow were meant to be strategically driven, using CC and class utility (I know, we use class utility in mythic too, but so fast that you don´t get to enjoy it).
The problem is that they are mandatory. You can't just skip them if you want to raid mythic, because you will pretty quickly fall way behind everyone else and the your performance will be lower. This never happened before, skills used to matter more than equipment or.. let alone, borrowed powers.
Now, I know that a lot of people who play every day for hours will laugh at this. But you know, I too used to be a to raider but life evolves; I can´t spend extra time out of the raids and you can totally feel a HUGE difference between that now a days and years ago. If you simply log in to raid, you are behind in a thousand mandatory grinds, this has a direct effect on your performance.
Player skills and group coordination were core essences in wow.. today they are not.
Why can´t we just have properly designed dungeons with 2 or 3 difficulty levels.. and that is it? no borrowed power grinding systems... This is the design of business men who wants us hooked up on a long list of mandatory crap you must do in order to perform. I did much prefer it when gamers were creating an amazing game where you would hook yourself in out of genuine interest and skill development.
I find mythic keys to be one of those silly designs. Smart business wise, poor game-wise. End game loot should come from raid bosses and pvp activity, period. Performance should come from player skills + gear from those bosses, not from borrowed systems.