Kayn Ult Is Broken

Kayn ult is completely broken. It takes a while to go off when you cast it. I play Kayn a lot and i dont know if this is a bug, but i think it is. Its really annoying because as an assassin i cant avoid the peel that is thrown at me. I become useless because my ult only works half of the time.

If someone could help me that would be awesome. Is this feature on purpose or not?