Is simply how -smooth- he feels. There's almost no delay, he's very free-flowing. Unlike a lot of other ADCs, he doesn't feel like a stutter-stepping turret. I think this is just underrated in why he's so strong. Sure, his passive is a strong thing, but I think the way he can move is... Well, very intuitive.
Or maybe it's just my imagination?
It is one of them. Look at how long it takes Varus' to cast his E while Lucian is spellslinging with fluid animations that change if he is moving or not.
Laughs in having self root on every skill besides E
His e makes it very effective when dodging assassin skillshots like 
q or 
w.
I mean I'll call him what he is. An anti assassin ADC.
That feeling of smoothness is just his passive firing off while his auto attack is cooling down. Theres a nice animation for using it while moving
Imo, some cast times need to be cut. The amount of times I've had the kill, but the cast time taking that few milliseconds too long is dumb.
