Great game, I have played it over and over again and have tried many different builds. Below is what I believe to be the best setup for easy passage through the Survival Mode for anyone who is interested. With this build you will cast extremely fast and destroy every thing so quickly, enemies will die before you see them on your screen.
(Note: put all skill points into fire or ice, don't waste anytime with divine, also don't waste any skill points on aoe spells.)
3-Master of Cold