I'm not getting the point here.
If you're willing to rerun the same dungeon 5~10 times at the same level with no reward, what's the difference from running different 5~10 dungeons to upgrade the level between running the same dungeon, if you're not getting any reward anyway and only what to boost ego in Mythic+ Leaderboards? Yes, I've read already the "we need to practice" excuse, but to me looks more like you're wanting a chance to do the same thing over and over again until you are able to cheese it, what doesn't sound so much of challenge more than a patience test. Now, it's good to keep in mind that some dungeons are impossible for some groups compositions. You won't ever be able to finish and EoA +22 with Tyrannical if everyone doesn't have a way to immune itself or the others for the Crushing Depths. Some things can't be perfectly balanced around 5mans content.
Planning beforehand, knowing the dungeon for the pulls you're/you're not able to do, knowing your CDs to foresight if they will/will not be up for the next pack/boss where you will need it, and coordinating all the CDs and the times needed looks way more challenging than just doing the same thing over and over until you eliminate all those problems just because you've run it so many times that all you need to do is follow the script of what worked from previous runs.