I mostly play as a dual wielding warrior and i gotta say that ice spike and wall of frost ( apprentice and adept ) destruction spells kill me more than firebolt and fireball even elemental resistance was working in 1.1
This is because of the slow effect and stamina drain of the frost spells, and it is the reason I use frost on my spellsword. It is extremely effective against melee characters.
No stamia = no power attack and no sprint
Slow = can't close the range/dodge blows
For frost spells IMO the damage is just gravy compared to these two effects. It is sooo much more valuable than a smidget of extra fire damage.