Easy way to buff Yorick
Just make his Q hit towers like trundle. You may have to put a damage reduction on it if it's too op right off the bat, but this guy was MADE to be a split pusher. The fact that trundle can split push faster and be useful in draining tanks in a teamfight while yorick is 'meh' in both catagories is why he needs to be buffed. His E slow is fine the way it is, just make him THE split pusher in the game. He's already forced to stay in lane with his passive, making his teamfights a lot harder if he doesnt have his ult or the enemy team kills it in 2 seconds (which doesnt happen as much anymore because of the hp buff). He's just lacking that oomf to make him viable.
. Yorick's problems lie elsewhere.