First things first.
Since the only thing truly kept through a Sion-level rework is identity, let's talk identity before the changes.
The way I always quickly describe Yorick to people in a short sentence is "The world's tankiest Assassin," though that's usually because we're in a game and don't have much time to talk. He is a burst mage that is tankier than 90% of the champs and also has these ghoul things that help DPS if they don't die to the burst. The fantasy is that he is an undying, bursty juggernaut gravedigger with ghouls who help him DPS. That is what I am going to try to preserve through this rework.
This Yorick, the Gravedigger rework is Degrtione's Sion-level rework.
(The mana regeneration is 8.375 (+0.566), it's just broken for some reason.)
This rework changes his burst (damage increasers, but with Titanic for the AA reset) from
- 575 (320% AD) (+100% bonus AD) (+12% maximum health) (+100% AP)
- 230 (+430% AD) (+100% base AD) (+11% maximum health) (+20% AP)
without either ult. A total change of
- -345 (+110% AD) (-100% bonus AD) (+100% base AD) (-1% maximum health) (-80% AP)
He is also more reliant on ghouls to DPS, as he has worse AS and cooldowns. As such, they last longer. You also sort of get to choose what you want with the fact that you gain stacks instead of summoning on each cast, meaning you can summon only one kind if you feel like it/hit a bunch of people with an ability. It also sort of takes out part of his lane bulliness because you can no longer use abilities on manions to poke with ghouls.
As with everything, exact numbers are changeable.