I've seen a Yi that did well in the jungle.
Then time came to leave the jungle. He couldn't do anything. Getting Madreds on Yi is like getting Zhonya's on Olaf. Sure, it has a nice effect, but it's a complete waste because it's not going to do very much for your overall performance.
In fact, I'd rather have a Zhonya's Olaf than a Yi. Yi's terrible, and Olaf could use Zhonya's while initiating.
Yi is a underrated Beast.