Riot fix this now

https://leagueoflegends.fandom.com/wiki/Untargetability

Since Yuumi's W is an untargetability you need to remove the synergy she has with passive stacks from because she is technically not even playing the game at this point and is perma hourglassed. That item is meant to be a risk play for burst mages but for yuumi it means free stacks without the fear of dying and losing them. Her laning phase is still too good for the late game healing and the fact that she has 500 aa range doesnt add any counterplay needed to kill her in most given situations. At least make her melee please so she cannot just free poke from autos and Q spam. She is the most unhealthy design since zoe.