All my mercs are currently still using pistols. In one particular sector, Igor faces off with some dude holding a rifle. Our positions are directly vertical, but a tree between separates us. In other words, the enemy is one square above the tree, and I am one square below the tree. Igor is proned, the enemy is crouched.
Igore does maximum aim with 2 pistols, but misses one shot. The enemy takes one shot, and scores. I quickload the game. Same thing happens again. I quickload again. This time Igor scores two shots. For experimentation purposes, I quickload once more, and once again Igor misses one shot.
How on earth can this be? What accounts for this? I understand rifles are more accurate, but surely it should be nigh impossible to one out of two shots with the pistols. Igor's marksmanship isn't that bad either, being placed at 78.

For whatever reason, if you quickload a save the exact same thing will happen. It's messed, and maybe I have it wrong too but I've done exactly what you've done many, many times and the same outcome will always occur. I guess the aiming algorithm is a bit more complex than just a random computation, but I did find something that serves somewhat as a 'fix' to what happens.
Instead of fully aiming every time, you should try each increment of aim, you might hit out of luck at 50% focus, rather than fully. That's a pretty dumb mechanic, though. Hopefully the 1.13 guys can do something about it.

It's kinda unfair how the whole thing works. But then again, the system feels very much different from Jagged Alliance 1, and I guess I'm used to JA1, where trees pretty much guarantee your safety more often than not.
Thanks for the comments and suggestion, anyone else?

I actually found it slightly worse with 1.13.
I had a situation where I was on top of a roof, firing with a rifle onto two enemies on ground level.
I killed one, but missed the other. He then proceeded to burst at me (I was prone on the roof, only the barrel of my gun pointing over the edge) and he hit me a few times, killing me.
I was proper gutted that my assumptions of cover where completely wrong, despite me thinking there was no logical way he could hit me.

Quickload? Amateurs...
Anyway, it is as kramhag has said - quickload will not reset the pseudorandom number generator, so the same thing will happen.
If you find yourself in a similar situation again, you might want to try stepping a square to the side, running up to the enemy and beating senseless him or just accept the outcome and take the shot like a man ;)
Btw, dual wielding in general is a waste of bullets and AP, especially if the particular merc in question does not have the "ambidextrous" characteristic. Get a single gun with burst mode (MP5k is ideal for the beginning, but even the Beretta works) instead.

It's better to spend action points on aiming than on dual weapons.

I dissagree. Reloading quick save will alter possibilities, you just have sometime to reload game many times but basically 'everything is posiible'. At least in JA 1 which I'm currently playing...
HertogJan Better aiming it's not always better choice. It's good only when you don't have many AP's left and you have choice 'HIT ENEMY or DIE'. WIth marksmanship good enough even normal aiming withou spending more points might be enough, if not load quick save...

" What accounts for this?"
That was quite funny (to express myself in a normal way).
Anyways... it's just a game, man...
Different thing can happen after a reload because the game has some random numbers in the shots, so the game won't be simple math and logic. Which are NOT fun. Sometimes you miss shots, live with it. To be honest, with simple pistols (especially with the S&W) you will miss ALOT. Those are crappy guns.