I suppose one of the solutions to this is giving the enemies more CC on PotD. Still I am not sure it is a good solution. I remember myself dealing with PotD solo well in PoE1 till first Petrify. And then all your efforts are invested into more and more Fortitude.
A better possible solution: as soon as you get immortality for (base duration)*(Int modifier), you get immunity to immortality for 2*(base duration).
They just updated their beta patch on steam to version 86 which fixes level-scaling. Might be prudent to test it out before moving forward with more balance suggestions if the level-scaling never worked to begin with. Link for those who wanna see beta patch notes : https://forums.obsidian.net/topic/98361-fixes-to-the-patch-beta-build/
