For those of you that haven't found this yet..
Most of the time your standard shot is a fireball, which of course melts mobs if you had used frozen shot. However I found a weapon called Darkbolt Blaster (below), which yes, hooray, you can fire to your hearts content and the mob will stay frozen in place :-)
Has anyone found weapons other than fire or Darkbolts? (Also my new weapon is fire based but has an AOE effect when it hits them! Gather up a group of mobs, run in a circle, and they all fall down ;-p )