Darius can't use his W on turrets. However, I do certainly agree that Yorick should be able to use his Q on turrets, but at the same time we have to ask - would his pushing be too strong if he could?
Allow me to explain: the ghouls and the maiden are already immensely powerful at pushing. I've killed an inner turret from full health in 5 seconds using a full army of ghouls and a Maiden. The only champion who comes close to this speed is Ziggs, who can execute turrets with his W.
I do agree with giving the ghouls some more defense, though. Facing anyone who has AoE is just stupidly annoying as him because they literally just hit 1 and all of them die.