Hello there bud
The difference between Ice Blast and Gust is in the Attributes.
Ice Blast with Attributes will do more damage then Gust.
Gust on the other hand has really good base damage, can be use on non frozen monsters (with the attribute) and can interact with Ice Wall for some cool combos.
So id say its a matter of how you want to play.
Both spell are really good.
If you want raw damage with the attributes, Ice Blast is your choice.
If you want good damage and an easier to use spell, Gust is best.
This is why i love the new patch, its gives you loads of choices.
Now consider this, why not both?
Base Ice Blast is still 400% without attributes, so you can put just one point in it and would still do loads of damage.
That way you could do something like place Frost Pillar followed by Ice Blast x3 and Gust x3!
Or keep rotating between the two.
Actually now that i think about it, that should bring your overall damage a lot higher then just picking one
Hope that answered your question …if not just say and ill try to put it in another way