You know if ADCs had a little more counterplay, assassins would be a little more relevant....
Take twitch ult for example. It turns his targeted auto attacks into highspeed skill shot projectiles. While it is hard to dodge by just walking around it, it can be dodged by well timed flash, blinks and dashes (all of which assassins are loaded with).
Whats my point?
Well, if all marksmen auto attacks were highspeed skill shots, assassins would have a better chance of facing a fed hyper scaling lategame adc by outplaying them.
Just a thought.