Well Yuumi scale very well with AP, all of her aibilities scale with AP. This means even with max AP the shield isn't useless. Additionally Yuumi AP is very good in low elo. If you can hit every Q and if your ADC isn't too bad you will crush the game.

I play Yuumi AP almost every game and can confirm that with a good ADC you can win really fast. As long as your ADC isn't getting countered by someone on the other lane you will be just fine.

If you do not understand why i'm taking some items/runes you can hover your mouse over the 'Note' Section. I explain a bit more detail about some choices.

If it isn't explained just comment and i might answer.

If you are losing, there is 3 possibility :

-Someone on your team suck. It might be your ADC who can't dodge and is 0/9 at 5 minutes or your top who fed the Atrox that is now crushing everyone.

-You suck. If you are missing a lot of Q, getting killed when trying to ward and using the shield after tanking skill shot it means you suck. I would advise to just play more to be better.

-The ennemies are full MR. It's one of yuumi's only weakness concerning stats. The issues should be solved with a Void Staff. But remember that if the ennemies are full MR, it means your ADC should carry.

1) Do not be afraid to wait before using your Q, missing is worse than waiting 5 seconds.
2) Yuumi doesn't have to move so use that time to look around the map for potention danger incomming.
3) Try to ward a lot. Your allies will love it. Just don't take too much risks.
4) DO NOT TRY TO TAKE DRAGON ALONE. It will not work.