The Yuumi changes make her a very strong buff, but her Q needs changes. And her passive, a little.
Ive played a decent handful of games with the reworked yuumi and the major complaints i have are with her Q and her passive. Ill get to her passive later.
Yuumis Q is a non-ability. It does extremely low damage with such a weak, situational secondary effect that it might not even exist. Theres a 0.5s window to proc an empowered Q now, and thats ridiculous. To remedy that, i suggest lowering the base mana cost to 40 and making its scaling per level 40/55/70/85/100. I also suggest removing the empowered version entirely, marking an enemy. Allies who attack the mark trigger Yuumis passive.
These changes make the ability actually usable and give it an important role without turning it into a nuke.
Onto her passive; Ive taken quite the shine to
over
. Relic shield is much more reliable and easier to proc, while promoting getting off WITHOUT putting you into extreme danger. I think a lesson could be learned here, mainly giving Yuumi a less champion centric passive that remains useful throughout the game.
Pop n block should be replaced with Bap and Block; When Yuumi kills an enemy or assists in a takedown she gains 30+0.1AP shield (Tripled for takedowns), up to 300+1.0AP. While attatched to an ally, any shields apply to them instead.
This would promote getting off while safe to stack up her shield in the early game, while giving her passive an actual use post laning phase when you no longer have the agency to move around on your own and your carry should be... well... carrying.