I agree. That is why when AKs-74U, a carbine version, was developed, vehicle crews and RPG operators were issued them instead of pistols. But it started appearing in the army only in mid-80s, later then game timeframe. Though, I do think that Xenonauts need some sort of starter carbine.
If you noticed, xenonauts use HE, not HEAT, ammunition for their rocket launcher, there is AP(HEAT) rocket in game files, but i'm not sure if it is used anywhere now. I do agree on general lack of power on explosives, but that's for balance purposes i guess