Turn Katarina's Q into a Skillshot
So she might actually take some skill. With Rito's recent updates changing many targeted Q's into skillshots, (I.E. Ryze, Veigar) I thought perhaps this could apply nicely to Katarina. With all of her abilities being targeted or AOE, she just doesn't have much in the way of weaknesses, other than hard targeted CC. It becomes extremely difficult to fight her, especially late game, as long as she can get 1 reset, it usually means another is on the way. I've seen Katarinas 1v3 or 1v5 way too often for her to be considered balanced in her current state. But the addition of a skillshot into her kit actually forces players to think about where they aim it, rather than just clicking on the nearest target in range. This could also apply to the dagger bounce, each being an individual skillshot aimed at the nearest enemy in range, which can be blocked, dodged, or juked, and the bouncing would simply end there. While this idea has some mechanical intricacies to work out, the basic idea remains a good one in my opinion, and it won't really decrease Katarina's power. Simply make her more difficult, hence the skill.

. We don't need to try and make everything a SKILL shot.
does take a lot of skill to get her full potential, which is why she has a difficulty level of 8.