Variance means nothing without expected value. So start here: https://en.wikipedia.org/wiki/Expected_value
In this case, you could look at what level of firepower you need to direct towards an Escher leader or champion in order to attain a 1/12 chance of taking them out. You will realize that, by using maximum firepower with a plasma weapon, you are essentially giving your opponent a free shot at you with a pretty decent weapon. A shot that they neither need to use an activation, nor make an ammo check, for.