And in my experience people who only focus on DPS and even manage to pull huge numbers, still stand in every volcanic there is and then blame the healer for dying. Have two of those in our guild, they care for nothing but damage and if you assign them to a task on a boss fight that is not to focus on the boss 100 % of the time, they complain immediately. I encounter them regularly in pugged mythic plus as well, last time was EoA +12 I think, this Demon Hunter kept dying on the last boss because he couldn't avoid the mechanics and blamed the mage for not pulling enough DPS, when the mage managed to survive and eventually pulled higher damage because of it.
Ever since wrath the focus has shifted so heavily on to damage that nothing else seems to matter. The mythic plus design reflects this as well.
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1: When I say CC, I mean stuff like polymorph, fear, hex, freezing trap, banish, not stuns. You don't have time to crowd control in mythic plus if you want to beat the timer.
2: You can completely ignore most npc abilities and just nuke them down with perhaps exception of +13 fortified, but even there I bet it's still about that aoe damage to bring them down as quickly as possible. I admit +12 is the highest I've ever run, but even there the tactic is the same.
3: They already scale to a point where players are unable to beat them, with or without the timer, that's the whole point, to always be able to push yourself further.