Every game that I have seen her in, she has rolled the other team. My most recent experience was a 18/2 kat in under 15 minutes. She killed the mid a couple times in the first few minutes, then just roamed and killed everyone else.
600k master points on 
She's either stomping your team or struggling to be relevant. There isn't really a solution for her or other assassins. Assassin update was meh for most of them, they only made the issues worse. They're funner now though,** which I guess is ok.**
Just take 
and point and click her. This summoner spell is overtuned a/f and I hate it lol.
She can be beaten, your mid laners just aren't abusing her right. Her levels before 5 or 6 are REALLY weak because even if she picks up a dagger, her shunpo refresh is still a few seconds. If you abuse that then she isn't that great. Also if you've played Kat before you know where the daggers are going to land before they do so. I will say she can proc thunderlords pretty nicely though.
KATARINA IN 2016 LUL
Maybe your team was a sack of potatoes or they were facing a kat main, or a lucky kat facing a sack of potatoes, there is no inbetween. I main kat. Every time i face someone, they underestimate my range and walk over my blades casually(i am a tryhard sorry), and they also underestimate her early game. Riot took a chunk of kat's late game and put it in her early and mid game. Just try to not let her CS and jump on her daggers. Try to predict her moves. Its pretty easy. DON'T PLAY RE-ACTIVELY, that is the biggest mistake people make against her
I've played a lot of Kat, both before and after her rework, and I just feel like she's not really relevant right now.
She can manage to actually win her lane now before six, but unless she gets really fed, she struggles to be relevant after the laning phase. Late-game, ADCs can just 1v1 her by standing still and autoattacking (especially if they have something to interrupt her ultimate), and that's not even talking about a real teamfight where they would have supports and tanks shielding/peeling for them.
A lot of mages do her job better, more safely, and from farther away. There's just no reason to pick her over a burst mage - except perhaps that she's fun to play I guess?
(But what do I know, I only have 119k mastery, unlike that other poster!)
