Firestorm costs around 400 magicka with the perk and most people won't even have that much in the first place. It only does 100 damage! I can use the wall spells for 2 seconds to do similar damage and 1/10 the magicka cost. Actually I can dual cast for one second! This is useless unless it does way more damage if the target is close to the caster. Does anyone know how much it does at point blank range? It should do at least 400 base instead of 100 to be useful.
Blizzard is pretty bad too for the mana cost. I only used the scroll once and I'm not sure if you have to channel it and if casting in both hands doubles damage. Still seems much better to just cast the wall spells or the expert level bolts.
The lighting one seems ok if it actually does what I think it does. Basically a channeled spell were you got to keep cursor over the target? 150 damage a second with dual cast seems ok. This just shows how useless firestorm is lol.