There was rest of team? They need our attention too? But kata was most pain. Just not fair damage and skillcap comparing to other champions right now. Any ap carry can be stunned or rooted, so this doesn't make her more vulnerable comparing to other ap midlaners.
But the others don't have to pop right into the middle of the enemy team to ult. When Kat hops into the middle of our team, I stun her, and she dies and cries.
Gotta go with those on Kat's defense here. Her biggest weapon is also her single biggest weakness. If you blow all cc on another champion while you KNOW that she's tearing you apart then you really are noobs. One knockup / knockback, stun or silence is enough to completely negate her ult and then she's without an ult in the middle of your team. I played against a team yesterday that had 9 total abilities that could stop Katarina's ult and all it takes is one.
You say a Diamond 1 can kill a whole team but not a Katarina with Azir, perhaps it's Azir that needs nerfs then. He can stop her ult with his ult or escape with soldiers. Not every game is about how many of the other team you can kill alone..