My Concerns about Precision, Manaflow Band, and Karthus

I'd just like to voice some of my concerns about what Meddler said about splitting the values in regards to both Domination and Sorcery (where it's about 70% AP/AD and 30% AS), the recent PBE Changes/Revert to Manaflow Band, and how they affect Karthus; a champ who's kinda still struggling in Season 8.

Starting with the proposed Precision changes, I'm not sure how I feel about the value split. While I get it primarily benefits champs who can utilize Attack Speed somewhat, Karthus's Autos are Abysmal, so it really just means he's indirectly going to be losing out on more Starting AP. This wouldn't be as much as a problem, if both A: Karthus's early game wasn't suffering as much due to the S8 changes, and B: Precision is Karthus's preferred Secondary tree due to both Presence of mind (which is good on Karthus because he can use it with his Ult), and Last stand (which works with his Passive).

As for Manaflow Band, there were changes to it so it would proc more often, but then they were reverted a patch ago. I was wondering what happened to that? I was kinda hoping I'd have an alternative to precision secondary for Karthus, so I could also run something like Celerity (for my Predator JG build), or Gathering Storm.

I'm just trying to make sure any proposed rune changes don't hurt Karthus's already struggling early game is all.

P.S. sorry if I mispelled anything, I did this on my phone :P