Thanks for the acknowledgement, and right back at you.
I think I generally agree with your points, and they definitely seem plausible. It is probably a bit too complex to completely unravel without some serious research in the subject, and you raise some valid arguments for your case. You might be right, and I admit that I don't know if you are or not.
On the mythic dungeon part: I think it is too early to tell how well it will work out. The thing about modifiers and scaling hp + damage is that those things combined with the existing mechanics can open up for entirely new situations. On difficulty 1 with no modifiers, you pop a cooldown when the boss does X. On difficulty 7 with a modifier, you might have to pop several cooldowns to survive it. On difficulty 15 you might have to try to dodge it, or LoS it, or kite the boss. So, in short, it might make the dungeon feel completely new to play through, even though the layout and visuals are the same.
I don't know if it will be as great as I hope it will, but hopefully it will
Nice to finally see some well thought out, objective, constructive argumentation from "the other side".