I think a way to help kalista without making her broken again..
Would be to change how movement speed slows interact with her passive. Right now, if she's slowed by a MOVEMENT ability it slows her attack speed to a crawl. A way to fix that is to make her jumping distance much shorter while still keeping her attack speed values at what they should be. Just a thought, though.
Edit: Another decent way is to disable her passive when she's slowed so she can still move and attack.