considering there are units in starcraft that die in 2 or even 1 hits, even a single dodge would increase their survivability by a ridiculous percentage. especially early game, this can easily decide the winner (similar to what evan pointed out with 14-18dmg instead of 16 for a zealot.. your zeal just gets lucky once and that zergling dies in 2 hits instead of 3, which is a huge decrease in that zergling's expected life.. and when it's 3 zeals agains 6 lings, that is a big deal)
don't tell me these are non-existant scenarios =/
i just don't see the point of this tbh. give me one good reason why this random chance cannot be replaced by something static and concrete that has the exact same effect over a long period of time AND over a short period of time