Katerina too broken

If enemy team picks a Kat, try picking champions with a Stun/Knockup or some sort of disruption for her Ulti. She's strong, but I wouldn't say broken. If your team has a bit of coordination it's easy to shut her down. At worst, ask your team captain to ban her.

Every time I see a post like this, I experience a perverse sense of satisfaction, knowing that the poster is the sort of person I stomp in pubs simply because they don't know the game well enough to deal with assassins.

For instance, if I had a nickel for every time I got into a game where neither team had a tank, just because everyone wants to deal the damage and get the kills...

Any CC stops her ultimate. Focus her in team fights.