I'm finding Permafrost extremely useful for complementing Shatter (which is the only ice-based attack spell that doesn't cause Frost),
mainly for keeping the more dangerous monsters from catching up with you while on the run from their melee attacks.
My only gripe is that its blast can't be used to put out fires. But yes, 8 skill points is a bit too much.
Also, Ice Storm and Frost Nova seem way too weak against higher level monsters, unless you spam 'em like there'd be no tomorrow.