I'm seriously getting pissed off with Katarina

Coming from a former Katarina main, something needs to be done about this champ. Yes I am making this post cause I just lost a game to a Katarina, but how it happened is beyond my fkin knowledge as to why it's allowed. I was 7-1 as Kassadin, she was 1-7. She went bot, I followed her, she killed my two team mates with like 200 health in 1 second before I could do anything, now this is where I have a problem. Off those 2 kills she got Zhonya's, and then she just snowballed out of control. You couldn't focus her cause she has statis and it's so easy to negate focus with statis. Then once she picked up a few more kills she got ludens, dcap etc. So my question is although she is an assassin, why is her scaling so poorly tuned?

I don't care about her q, w, or e scaling. I'm talking about R with the 750 base damage 250% AP ratio and 375% bonus AD ratio. Who at riot thought it would be a good idea to give an AOE spell that much base damage and scaling? Let's look at Kassadin's old scaling for example. His Q did 220 + 0.7 AP, E did 280 + 0.7 AP , and R did like 120 + 80%. I have no problem with this as it is mostly single target damage except for E, yeah he's a mobile assassin and he's very slippery and such, but so is Katarina, and I'll tell you why, Kassadin will usually go in kill someone then get out cause he has Riftwalk, well with Katarina's passive she can technically use Shunpo 5 times in a short window when you're teamfighting, assuming you hit everyone.

It has 700 range, (old kassa range), Does damage, and gives damage reduction. All of this scaling and utility on an assassin is obviously not healthy as Riot is trying to prove with Kassadin, so why does someone like Katarina get all of old Kassadin's scaling in 1 ability? Sure you're able to CC it, but what aren't you able to CC in this game except unstopable force, and assult and battery, a few others too that I can't think of ATM. Anyways my point is that Katarina's ult scaling needs to be toned down, it use to be 150%AP, god knows why they brought it up to 250% when she was already melting people pre nerf.

P.S., you can say CC her all you want, it won't matter since it's solo queue and everyone wastes their CC at the beginning of the teamfight, and there i am the idiot who saved his Null Sphere to silence her ult, but nope I can't even target the fker cause she jumps somewhere new every 2 seconds, and I end up accidentally targeting it on someone else, god forbid she also has zhonya's and avoids all your damage all together.

TL;DR Yes I'm mad that I lost to a trash Kat, you can say well " she beat you so obv she isn't trash", trust me the way she was playing all game was trash. Fact of the matter is all you have to do in a teamfight as Kat is stand behind the team hiding, wait for the enemy team to waste CC, shunpo in the press R, THAT'S IT. No positioning required, no thinking, just braindead button pressing. Her scaling needs adjustments. Base health reductions won't fix any problems and she does too much damage and her staying alive isn't the problem.