Quote from Juno;99407:
The reason ice mastery is an arguing point is that hailstorm really needs to be able to ohko or 2hko to be effective. Ice spear is spammable and doesn't need damage as much.
I disagree with spamming Ice Spear, I always full charge it because the damage is almost on par with Thunder/Fireball (83%).
But since Hailstorm always knocks back at full charges, then I do see how it can be more useful than Advanced Magic depending on the situation. If it also ignores protection for Criticals, then it might even beat Blaze on single-target damage (even if not, it's much easier to use).
Do the test server people have access to Shadow Wizard Hard? I'd like to see it in action there if possible.