Can we lower the hitbox on Katarina's daggers please?

The dagger isn't the hitbox you need to be aware of, it's when Kata picks up the dagger that is hitting you.

They basically put Kata's old W on her passive when picking up a dagger, and her old W was about as large of a radius as a Lux E.

So if you ask me, I see no problem; generally you want to avoid a knife throwing crazy lady anyways, so just keep your distance.