As an assassin player probably why kai sa is harder than draven, infact he is way to easy even if i haven't played him in months. Its just that he is not hard as in pc.
You gotta be a Draven wizard. Looking at his mastery curve there is a stark difference between a players first game as Draven and a Draven player. His skill floor might not match LoLPC, but he is far from an easy marksmen to pick up.