I've changed shotguns to be less accurate at medium distances. They're still very good at close combat. We'll see how it goes.
Hm. In FMP 1.9.3a/b both snap and aimed shots have a max range of four (4) and a dropoff of four (4). I suspect you incresed the dropoff-value. How much?
This is only (maybe) a problem with the AP Shells (non-pellets), in my opinion. Even at max distance before dropoff pellet-rounds are not too reliable, since a lot of the pellets miss their targets. Standing next to, or maybe with one tile in-between you and the target, Shotguns with pellet-ammo are just awesome! But farther than four tiles away I'm actually preferring the Assault Rifle with auto-shots (4 bullets) instead.
Shotgun AP Shells is more a competitor to the Auto-Cannon, in my opinion (40, 50 with AA, power vs AC's 44). And the only reasons for using Shotguns with AP Shells instead of the latter is if your soldiers are too weak to carry it, if you're facing very early (before AC is available) Snakemen (Shotgun 40 power > Rifle 30 power) or that you haven't researched it yet! The reason being the low range of the Shotguns.
Obviously, Grenades/HE solves everything... but that was not the topic here!
Sincerely
Kjotleik