why hasn't yorick had his range nerfed?

Because technically? Yorick's fine. If anything at the moment he's undertuned for almost any lane. He's an excellent lane bully, but he has heavy skill matchups and a lot of hard counters. He's if anything, undertuned now due to past nerfs.

There's better lane bullies (Heimerdinger), there's better tanks (most of top-lane), and there's better Ranged bruisers. And there's better tank bullies (Cho'gath, I swear...)