Also, try to take advantage of you're stats by equiping items that increase you're magic, and maybe even speed, so
theif's hat (for speed)
wizard rod (for mage)
Sorry, I can't give away my complete secret on why they are so powerful, so experiment with them it'll will be worthwhile

i just have them set up with mimes and all lv 99 and imune to death then use deathlv3 and it kills everything except your own men.

The optimum party is three calculators and two mimes. That gives you nine calculation spells per round of guys. That being said Calculators and Mimes true powers come when you use them in tandem (and in that ratio). If you change the ratio the max you'll get is eight.

1 Calc & 4 Mime = 5 Calculation Spells
2 Calc & 3 Mime = 8 Calculation Spells
3 Calc & 2 Mime = 9 Calculation Spells
4 Calc & 1 Mime = 8 Calculation Spells
5 Calc & 0 Mime = 5 Calculation Spells

Whats great about this is if you haste your Calculators and raise their speed it all becomes that much more effective though a team of monsters will hardly last nine properly done calculations.

yes someone who really know the system now please tell the person who don't know how to get them how
...i forgot...

i know i am necroing but i have to say something
ok if you get you mages well made then when you get the calculators and you have them build up exp and 3 and have your charactors lv 99 you can hit everything with all of your spells thus effectively ending the game quick speed doesn't matter cause when your enimys are dead why you got to be fast and it is simple to use them just make sure all of your party(fighting in the game at that point) are lv 99

Good - If you know every last spell/magic ability in the game
Bad - because they take like 3x the time to act compared to a regular character.