Just some feedback regarding Yuumi from a D2 support
TL;DR: She is actually fine and doesn't need major buffs.
Can confirm players will take quite a bit of time to get used to her. Both Yuumi users and her teammates.
Her Q damage might come off as little, but it is a guaranteed-to-hit lane harass -as long as ADC is not too far- and slow with insane range, easy to control (except when it lags randomly). And you can do it without being in a risky position. Buff the damage and she will be too strong with a little sync.
People don't realize that her Q increases the engage range/threat of a Master Yi or any champion by a lot. Stay just in his sight range. Yi / Whatever champ just has to walk towards you while you get hit by an impossible to dodge Q and that's the end of you, you simply can't escape. It's a skillshot with already long range that INCREASES while the ally is walking or running. If the skillshot has 2000 range, and a high speed champion or gap closer runs during the 3 seconds in flight, the actual range can be like 5000.
Her teamfight potential is underrated. Here's an example of a usual situation:
- W+Q Slow enemy for initiation (maybe ult too)
- W+Heal Ally 1
- W+Heal Ally 2
- W to detach, AA an enemy + W to Ally 3 for shield
Theoretically you can execute all this instantly, but doing properly in the middle of a teamfight requires good awareness of everyone and if people are clumped it's not easy.
About her R, people saying "It's a worse Sona ult" couldn't be more wrong. Her range is a lot bigger, the first proc will disable banshee's, any spellshields or Malz passive, and you have the opportunity to reposition if you miss anyone or to root the rest of the enemies.
Just sharing my 2 cents since I predict people will keep complaining.
Update: Her very early game is definitely her weakest stage, with pretty long Q cooldowns. It's not a lane to play aggressive early.
Update 2: Tbh I think the movement speed buff from E has actually too much Scaling. I was giving my Udyr almost 100% movement Speed buff without full build.