Her banrate increases with ranking. Her lategame assassination kinda has no counterplay, since she can onneshot squishies from stealth really quickly without having to use her W or Ult, which has a much, much lower cd lategame compared to its giant early cd.
Also, because of how line of sight works, you can hide behind destroyed towers to get in range of someone without them knowing.
Despite that tho, her early game is extremely abuseable, as she can't fight anyone without getting the drop on them and lacks her stealth. Even Kayn can bully her easily, and it's not practical to always expect help from your team especially in soloQ. Legit if one of your buffs is being directly contested at that stage of the game, it's almost always best to just give it up.
They're going to nerf frostfang on AP junglers first before seeing if she actually needs nerfs, which might be the case since they'll be buffing runic echoes as well.
Personally, I'm expecting her passive hp regen to be the first thing that gets hit, but I could also see her E % dmg or ult dmg at later ranks taking hits as well.