[Snake]

I'll probably be bombed here by you two, but eh, generally the battle fields aren't that big. Not in a PvP view.
And ways to kite people who gear up against knockbacks (Hi Spiked Threads.) are almost none without Cripple Leg or any sort of Slow/Ice Tiles. (Magic Gunner's Parting Shot aside.) for ranged people.
Also there's a lot of gap-closing skills, alternative movement skills and movement enhancing skills (like Chaser, Charge, Shukuchi, Blink) as they eat all movement impairing easily.

;tl'dr Why not a cripple to 1 square movement? Archers aren't melee brawlers and have to play dirty (kite and trap, mostly) to win.

But well, that's just what I think. [strike]And will surely regret to have said, someday.[/strike]