User blog comment:ClariS/Why Xerath's Passive is Bad/@comment-5830369-20130318145725

Sometimes Riot design is weird. I would recommend you to read this article:

http://www.reignofgaming.net/blogs/hashinshin/23587-the-difference-between-the-old-champions-and-the

Riot had this ability planned before they thought of Xerath, so I guess they just stuff it into him for fun...