Yordles are balanced

I play in gold. 2 games ago I got destroyed by a guy who basically rushed yordles. He even had two of them on one star. At the end of the game he only had 2-star champions.

So I did the same. I just bought yordles whenever they were available, levelled up, added some sorcerers and later on shapeshifters. Before the last fight I had 1-star Gnar and Kennen and a 2-star Tristana. So practically 3 useless champions. For the last fight I managed to upgrade Kennen. Needless to say, I won.