Quote from Jiangshi;1228498:
I had a thought and wondered if it was possible to deal enough damage with a single fireball to kill MA groups, assuming you got max/best possible reforge and enchant rolls.
You can wipe out waves 1~2 with a critical fireball. Waves up to around 4~5 can be effectively cleared with two critical snap cast fireballs.
Thunder is preferred. While the area of effect is significantly lower, the standby period allows you to easily pull off double thunder (with some minor pet control to block enemies with mana deflector).
Ice spear has excellent synergy with Blaze, which is a more ideal way to tackle NPC.