@Riot here's the deal... Karthus REALLY needs his W buffed.
Seriously, the slow on that ability is barely noticeable, especially with everyone else having a dash of some sort. I was landing it on a Heimer and even then, there was no possible way I could catch up with him at all. Look, I know that Karthus is supposed to be a Hyper-Carry and yet have to rely on his team for him to carry, but Karthus is supposed to excel at Dueling with his Double Damage Q's as well as Teamfight's with his E and R. As for his W, he's supposed to be able to use it as a way to
- Peel for his team
- Initiate with the slow and MR shred
- be able to punish those who get too close
it's just that Karthus's W feels so lackluster, it's barely worth as an ability, I really hope this changes in the near future.