@Riot Karthus Buff After Rylias Nerf?

According to OP.gg, dropped from a 52% win rate to a 47% win rate. Combined with his low pick rate this data is alarming. He had a high win rate before because only dedicated players wanted to play him enough times to get good with him. And the only changes that were made that affected him was the nerf and the removal of bonus ap on blue buff. If Karthus had a higher play rate this drop would make since, but only small percentage play him and not even they can keep him above 50%. Straight buffs would not work since Rylias was made cheaper so he can buy it faster, but Karthus benifited from every stat on Rylias, now nerfing (an actual core item on him) nerfed him as well. Maybe reverting the slow on his W could help him.