Can Cass's ult be fixed?

As much as I really enjoying ulting an enemy champion who is in the middle of it's range and running directly towards me, then seeing it not hit them. It seems to happen primarily with high MS champions.

It seems like it sometimes decides who it's going to hit at the start of the cast, then double-checks at the end of the cast, but doesn't add new targets.

Possibly either fix it to only check at the end of the cast or just remove the cast.