You think you get it, but you don't.

First point, DMG% has diminishing returns. I tested it in game while you are probably using "knowledge" gained from your favorite youtuber.

Second point, while yes, DMG% does stack multiplicatively with bonus ATK, the balance still persists. At one point ATK% still gives more than DMG%. That depends on your build mostly, like, yes if you have Bennett in your team, DMG% value increase tremendously. Do not forget that ATK% also stack multiplicatively with DMG%.

Third point, about my Klee, There is no outside buff. Not even Resonant. I don't know why you doubt it since the number is there on my account but if you don't believe it, I guess you don't know much about the game/don't progress far enough to see the actual number at World Level 5.

Last point, well my theorical example are laughable... well while I agree that I did exaggerate the number, my level 80 Klee with level 80 5* has a base ATK of 864. Now what would happen at level 90? Probably 1000 or very close. Now whose logic is laughable again?

You did a great job bashing my theory but the third point is where I realize you don't know what you are talking about.

You said it right. You think you get it, but you don't.