I can't even tell if it's either Yorick needing a bunch of buffs to have strengths other than just his ghouls, or Yasuo needing a bunch of nerfs to be a lot less obnoxious to fight against.
It's that Yorick, as a minion based champion, gives Yasuo even more mobility in combat than he normally has. You aren't going to win that fight,any more than you would against (oddly enough) Nunu. It's a very poor matchup for Yorick, and there's very little you can do on your own other than swap lanes.
yasuo's E benefits from the minions yorick summons
yasuo's Q benefits from the minions since they'll auto attack him if he lets yoricks E hit him.
yasuo's passive lets him receive 1 shot from yorick and not receive damage
yasuo's windwall blocks yoricks only projectile attack and both cooldowns are about the same length
yasuo's fighter mechanics allow him to basic attack your ultimate and remove it from the game efficiently due to how criticals work and the fact that your minion does %hp damage. yasuo doesnt usually build hp and his phantom dancer allows him to prevent a portion of damage when solo fighting.
yasuo's E lets him dash out of yoricks W
yasuo's enhanced Q can hit yorick easier because of how big yorick's model is.
yorick has no real crowd control.
