First, the AI.
Honestly, the ghouls and maiden feel lackluster in lanes.
They only feel like they function properly when Yorick is running through the jungle; a shambling horde following behind their undead master.
Once they enter lanes, they just turn into glorified creeps, which feels bad to use and annoying to play against.
I realize that the whole "splitting both lanes" is something you wanted, but no.
The maiden can push lanes like no other, but dies quickly when it runs into a tower, dealing only a couple hundred damage to the tower. You blow a major combat spell, with a massive cooldown, to push a wave to tower.
I recommend removing the "run it down mid" mentality from their AI.
Second, the distribution of power
Most of the power in this kit is placed in the damage of Last Rite, which is the least interesting part of his kit.
Ghouls hurt, but are extremely stupid, not very fast, and squishy as all hell.
His W is pretty nice, but anyone with an auto attack reset (most toplaners) or decent attack speed (most adc's) can break out in less than a second.
His E doesn't feel like it does anything.
His ult works great if it fights with Yorick, but suffers from the same problems as his ghouls; stupidity, squishiness, and slowness, in addition to not doing much damage on its own.
Fighting him could be so much more epic. You could be fighting the commander of an undead legion. You could be trapped in a pile of corpse. You could be bombarded with soul consuming miss. You could have your soul sucked out by a goddamn wraith.
But no. He just hits you with a shovel.
The q should feel good to use, but not at the price of hours other spells.