It has the longest cooldown in her kit and longest rank 5 basic spell minus hawkshot which is a scout tool, which i do use ice wall as a scout tool more often than an actual wall because it gives off massive vision around it and even more as you rank the spell up---
the reason to why i don't think adding an anti-mobility effect to it would make her op is because back in season 1 that is what the spell did was anivia walls someone off to stop their path or they flash over it --- plus i'm pretty sure riot would be on board for adding more anti-mobility (which they stated recently) and they finally added the anti-dash / jump mechanic to event horizon which is half the cooldown of ice wall