Thanks for the correction.
Ray of Frost still requires a hit roll causing the average damage it causes to be closer to 3.25 for a total of 96.5 there.
If you want a theoretic best division, it probably would be something like this:
5th, 2nd, 2nd, RoF
5th, 3rd, 1st, RoF
5th, 3rd, 1st, RoF...