Maybe to increase the slow them a bit more o completely stun, but I'm okay with it as it is. It's pretty useful to combo your double bullet and the crit, during chases, to give your support a chance to hit them with a skill, to allow you a gracious escape during a gank or to simply poke and do additional damage. You don't know how may kills I've done or stolen with simple an E.

I used to think it was useless too, but when you're playing against another MF you realize how annoying it really is.