As the game is out now for a longer time, in addition we have the growth Stat, I was able to do further research on the DMG formula.
After a lot of testing with a maximum of 1360 physical Attack there was no change in the actual Tier 1 DMG formula.
Because of this I claim, that the Defense that is needed to reach 100% mitigation, is based on Level instead of the Attackers Attack.

Offical Lv40 – DMG Formula

DMG = DMG x (1-(Defense / 12000)

Please note: This formula is for Lv40 vs Lv40!

I am going to remake my DMG Formula video soon.
I assume that Lv45 needs 24,000 Defense and Lv50 36,000 but this has to be confirmed on the Level Patch!

Overall this makes low Attack stronger compared to before but defense cannot be countered!