They did not sharply buff everything in Kai'Sa's kit.
They upped her auto range by 25.
Same with Q range.
Then they lowered her ap scaling on w by half.
The scaling that would go into w was added to her Q. Making them deal equal damage when building AP. Q also got an execute on low health minions. And e evolved got a movement boost.
Furthermore afterwards they even nerfed her Ad.
That was all they did to my knowledge.