So, huh... you're basically saying that real-life military/LE forces don't dual wield pistols because :
1- ranges are often to big, and
2- dual pistols would be too much firepower
While your arguments may not be outrighlly wrong, they're not the reason why dual pistols are not used IRL :
1- extreme close range encounters DO occur for LE units (esp in buildings... and they are not few in UFO:AI !). I wish I could find you that report revealing that many gunfights involving police take place at about 3 METERS, and even then, many shots miss their target because of lack of aiming. What's more, every miss is a risk of stray bullet hitting an unintended target (read "civilian passer-by").
Thus, even the extreme close range (and its supposedly lower need for aiming) cannot make up for the ultra-poor accuracy of dual wielding.
(And BTW, 10 meters is more than the upper end of extreme close range : it's short-medium range for a pistol firefight).
2- If dual pistols are overkill for LE units, what would they NOT be overkill for ? Military ? They have access to better weaponry, namely machine pistols, SMG, and if encumbrance matters, PDW (tor instance, the H&K MP7 is only a tad larger than a full-size pistol). All of them are more accurate, faster-firing and often more powerful than dual pistols. They are also orders of magnitude easier to operate, while pistols are usually not fully ambidextrous (and many aren't)... and DEFINITELY NOT designed to be reloaded or unjammed single-handedly !
So to sum up, there is NOTHING dual pistol do better than a specialized weapon can. (the same goes for the Desert Eagle, but that's an other story...).
They *might* have a tiny bit of interest if you were some poor citizen caught in a civilian war with no resources to get better weapons, but for a world-funded specialized military unit, they are not even worth thinking of it.