I really like what I'm seeing here, so, if it's alright, I'd like to give my two cents on each proposed change. Hopefully this doesn't come across as too critical in the spots that I feel might be.
-
"Ghouls now die in two hits from Runaan's Hurricane bolts instead of 1 hit." This I feel would be a really great buff - not one that would be immediately noticeable, but definitely one that would give Yorick an edge against certain champions who would otherwise be able to care less about getting hit by Mourning Mist.
-
"Ghouls no longer pause for a moment after jumping with E marked targets." I'm not a hundred percent sure how to feel about this, because there's kind of two sides to it. For one, functionality would play out a lot better for Yorick if his Ghouls didn't hesitate to start laying into his Mourning Mist targets, but at the same time, the Ghouls do a tremendous amount of damage on their own even with the pause, that I'm kind of 50/50 on whether or not this would be a good change.
(seriously speaking, I've seen Bruisers like Jayce get torn straight down to %15~ health with one Mourning Mist under his own tower. The little guys are brutal.)
-
"Ghouls spawned from the Maiden of the Mist will follow her until they jump at an enemy marked with Yorick's E." This, I'm also not too sure of. The Ghouls really only follow the Maiden if they're summoned by it while it's being used for split-pushing, elsewise the Ghouls will just follow Yorick himself. This could be sort of changed to fit, but it would probably involve a buff that would certainly overtune Yorick, which is to say, allowing the Maiden and Yorick simultaneous Ghoul caps while nearby. But, that's just my thinking of it, and I could be totally wrong from an objective standpoint.
-
"Ghouls will now only leave Yorick to push down a lane if allied or enemy minions are nearby (normal vision range, roughly)." This, I can feel safe to say would be more damaging to Yorick than helpful. Although, that is still subjective, as I've not played anything but the Yorick whose Ghouls only break off of him by entering combat, it still seems like an AI change that would make playing Yorick a little more unwieldy. I don't think anybody would want to lose their Ghoul army by clearing a ward near top lane just as a large minion wave piles up nearby.
I definitely enjoy the thought of the first two buffs. Sort of iffy on the second one just a tad, but all in all these are great ideas.