Make Kalista's Rend scale off Bonus AD instead of Total AD.
That's basically the primary reason Kalista can get away with building Hurricane so early and still wreck people.
As Rend is now, it's so many times better than Twitch's E that it's almost sad to see. It has Total AD scaling instead of Bonus AD, no stack limit, has a slow attached, refunds its mana cost AND resets itself if it kills a target, and costs significantly less mana to begin with.
(Also make its damage cap against monsters 390-1000 based on Kalista's level. Remind me again why we have an ADC that can out-smite Smite with a basic ability.)