Honestly just rework her at this point, she only has 2 Damaging Abilities (Q, E), her Passive reduces her Basic Attack Damage to 90%.
She has way too many tools for Pro Play to be abused (R being one of them, W Passive Partner Damage) and unnecessary amount of Utility that doesn't work with her Character or Theme (W granting free scouting and vision, making her ungank-able in the right hands).
- Her Q is nothing special.
- Her W doesn't work with her Kit.
- Her E is sort of okay but it doesn't work too well mainly because of how fast paced the game has become, as well as the fact that everyone has burst now a days regardless who you play.
- And her R is just a free GA.
Honestly the best way to preserve her imo is just make her work similarly to Lucian. Keep her Playstyle of being Mobile, requiring to Kite, but give her other tools to be able to duel better.
Here's a few rough suggestions...
P: The same but Backward Dashing is further and Forward Dashing is shorter. Remove all other parts in her current Passive.
Q: Keep it the same but add 2 things; Make enemies get Stunned when they get pierced into Terrain and make it so that her Q pierces through all Units which add a single stack of Black Spear to all Units hit.
W: Still working on it.
E: The Same but when she detonates the stacks she Slows the Enemy (The Slow is based on amount of Stacks Detonated), and Grounds the Enemy (Duration based on amount of Stacks Detonated).
R: Still working on it.
The general gist is to give her the tools for timing abilities in the right moment to be more rewarding. Imagine she Throws a Q into a Kha'Zix who is ganking her, and when he Jumps, she Activates her E and then he get's Slowed and Knock-Down due to being Grounded.
Tbh I kinda wish both Varus and Kalista could get like a massive VGU, both of them feel really unrewarding and generally quite weak due to not really having their own niche as to why you would pick them specifically over any other Marksman.