So the Yuumi nerf...
I know a lot of people were saying this was RIP Yuumi, but after playing her I think it was a whiff by the balance team.
During the laning phase the slow isn't really big, because you're just looking to poke the bad guys. It's not like the slow will trigger an all in like a morg binding. After laning phase the q slow doesn't feel like a huge part of the kit. It can sometimes let you escape or catch up to someone who is running, but it really doesn't feel much different in practice.
If they want to do a change that will impact her don't give her a point in w to start. It would make a huge difference in the early lane if she doesn't have controlable q's at level 1, and doesn't have sustain at level 2. (this is assuming q>w>e skill order level 1-3).