[Rework Concept] Yuumi does not need buffs she needs a rework.
I've intentionally tried to keep out numbers as much as I could because this is more of a concept/general idea that I had that would not only make Yuumi preform better, but feel better to play. As well as allowing her to make more plays, and open her up for base stat buffs.
Her passive should give her a stacking shield per auto up to a cap.
Every auto adds a low % of her AP to the shield. ( With a cooldown. ) Yuumi gets attack speed for every few points of AP.
Yuumi auto's cannot do more damage then her base damage, and do not proc on hit effects.
After being near an ally for 3 seconds that ally is marked (visible to Yuumi only), and she can attach to them. Upon attaching all shields on Yuumi get transferred to her ally (up to a cap), while attached Yuumi can cast all skills (movement skills will detach) and takes a % ( 30 - 40, maybe? ) of damage that's done to the allies health.
Her Q missile should lean into the mouse instead of following the mouse, and get increased projectile speed based on Yuumi's movement speed at the time of launch. ( This means you can boost it with your E, and by building MS items. )
Her E temporarily increases her own movement speed as well as her hosts, and consumes a % of shielding to heal the host ( + base heal value ).
Her ultimate should stay the same.
Hitting an enemy with her Q will reveal them and give % increased damage to her hosts next attack (as well as procing on-hit effects) on the champion based on Yuumi's AP.
What do I wanna do with this kit? I want to open up Yuumi to more impressive play, as well as more play that just feels good not only for you but for your team as well. I also wanted to introduce more risk/reward thus making Yuumi think about who she has to attach to... think about positions... etc.