The option might be introduced in coming game updates
Despite the bounty of new options introduced with the Second Wave free downloadable content, fans of XCOM: Enemy Unknown have been asking for a possible change to alter the currently fixed hit chance for shots.Rock, Paper, Shotgun asked lead designer Jake Solomon about it and he answered: “I probably should have done that, actually. Sorry. I think Civ includes an option, don't they, where basically you can either have things be synchronised where every single time, even if you reload, the same thing happens, or it's random. I could probably have made an option where the results weren't synchronised.”
Despite the fixed result, XCOM: Enemy Unknown remains one of the most engaging titles of the past year and gamers can also get the Slingshot DLC in addition to Second Wave.