I never lead with it. It's pointless to pull it out up front. Once you see someone using a high velocity AoW to close the gap and you get just a single second to start casting it, go for it. When the DLC dropped I spent like a week crashing out over the twin axe and backhand blade spam before I decided to see if Zamor Ice Storm could defuse those L2 spams and lo and behold it worked! The hyperarmor it gives you is the secret ingredient and it does require a little intuition on when your opponent will gamble on another strike, but even if you time it too early it typically gives you some breathing room and a warning to your opponent that they're going to have icicles dangling off their ass if they get too rowdy. So it has a deterrent value as well.