I went through this the other day. Loves me some Yorick. Just take towers = win, screw kills.
Sadly you nearly always have to go Resolve as most other options aren't great but this does help you overall.
Grasp is the only main rune you can use, other 2, one is for support the other CC, Yorick has neither.
Next Demolish - for obvious reasons (I think this will be abused and nerfed, full HP tank cho can take a lot of health from a tower with no minions about, if they removed the HP scaling on it and just make it scaling, that would be great as then it's intended for Yorick, Nasus and alike).
Iron Skin/Mirror Shell - Change based on your lane opponent. With Q's healing, you proc this easy... once you have level 5 at least.
This last Resolve stuff is all pathetic, 0.2% of your health, perminant increase or not, Yorick isn't building HP tank. Second Wind.
Then this is where it's confusing. What you pair it with.
I don't like Precision or Inspiration here to pair with.
Domination - Ghost Poro and Ravenous Hunter, the former to help split, the latter as I presume your ghouls and Maiden all count in this, healing you as you fight.
Sorcery - Harder choices. Manaflow Band and Absolute Focus will help in lane, Ultimate Hat allow you to summon maiden more often. Absolute Focus mentions nothing about being out of combat so extra AD when full health taking turrets?
Alternate idea.
Have Inspiration as main Runes. Summoner Specialist. Use it to take smite to secure Herald or objectives later. Biscuit for lane sustain. Minion dematerialiser to help push waves. Celestial Body for 100 health bonus, only 8% damage reduction? Fine with that. Then with Resolve and get demolish and Iron/Mirror. Bit more troll split push but might work.