User blog comment:Willbachbakal/(Champion Rework) Kassadin, the Void Walker/@comment-24385282-20150301005547/@comment-24385282-20150301195021

You say Kass would "rather do this," but what if someone went Kassadin purely to negate the enemy ADC? If he stands close to them, switching targets won't have much effect and with the increased movement speed, it'll be hard for an enemy carry to be able to get even a single basic attack off before Kass repositions himself to be in front of them again. He's intended to be an assassin, but that doesn't mean people couldn't chose to play him a different way.

He's like a small but hyper-mobile Wind Wall, easily moving to block any ranged carries from doing much at all, negating entire ultimates like Ezreal's or Nami's which would otherwise have huge impacts on the outcome of a teamfight. He can even stand between an ally and an assassin like Katarina, negating her ultimate almost completely, or dash in front of an incoming Chum The Waters to make it useless. And all the while, the more projectiles he's blocking, the longer he can continue to block them.