He is not extremely good, as the jungle meta has moved in a direction that makes him even more vulnerable to a smart gank than he used to be, but if you play safe with regards to the enemy jungler you can easily dominate. I only have experience against Yorick, but in my opinion he is one of the few secret OP champs if you take the time to learn how to play him. It's quite easy to tell if someone knows how to play Yorick or not, and the difference it makes on the game is staggering.
He's not faceroll OP, but if you play him correctly you can easily 1v3 during the laning phase. On top of that the changes to snowballing and itemization have improved Yorick's late game power curve. If you get the ball rolling early enough (which isn't particularly difficult) he can be harder to deal with than a Nasus with 1k stacks. He still requires his team more than many other champions, but if your team is on the same page as you are you'll do just fine.