he is new and people do not know how to fight him yet.
That isn't really relevant here. Knowing how to fight him is way, way less important to his winrate right now than learning how to actually play him. We always see winrates increase after champions are released, no matter how much people have to learn in order to effectively play against them. His winrate will go up. It's uncertain how much it will go up, but it will go up. It's not staying at 44%.
It's worth keeping in mind that this kind of winrate isn't unusual for reworked champions. Poppy released to a terrible winrate too. She ended up being broken.
That said, I don't personally think that the Yorick rework left him very strong, and I'd be interested in seeing some buffs that give him some more general power.
His E currently does 15% of the target's current health making it less and less effective as the fight goes on why not make it 15% of his max health
Makes spamming it for poke too effective, and poking with a ranged skillshot is definitely not supposed to be his playstyle. I can agree with buffing the skill, but making Yorick a poker isn't something anyone wants.
His ultimate is stupid in a team fight unless you land your E the maiden will attack anything it sees like minions. why not give it a better Ai.
Sure. Increasing his control over his ultimate is generally a good idea. I'd personally suggest giving him the ability to use the R key to toggle whether the maiden follows him and attacks his target, or whether it tries to push down a lane. The biggest problem I always have with him is that I can't use the R to win a fight without losing the maiden down the lane, even if I know that it can't possibly accomplish anything with the split push.
Why not give it the Cassiopeia treatment while in the w you can't use a dash but maybe you can still Flash.
That would effectively make it a 4 second root against any champion without fast attack speed. That makes it way too effective at hosing out certain champions without actually making it any better in teamfights (the place where it really needs help). It's fine to expect him to throw it after movement abilities have been used. That's not a new requirement, and it's not unreasonable. What would be better is increasing its ability to take punishment in a teamfight, or lowering its cooldown so that he can feel better about using it to force mobility cooldowns to be blown.