Fallout's weapon balance was poor at best (lol all AP ammunition/14mm pistol), and the odd change to damage mod isn't going to change that.
If you want to make the FOnline combat system something other than a polished but nostalgic turd, it needs an overhaul. Get feedback from both PvE and PvP players about what they do and they don't use. Then go through each levelling stage:
1-3.
3-6
6-9, etc.
And then work out what guns you want them using and crafting. If something doesn't get used, it's crappy. If everybody's using one gun, then nerf it or improve the others.
I'm not interested in PvP, but they're the best measure of what's good. Their super efficient mentality means that if something isn't good, they'll ditch it. So when they say a gun sucks, they're right.
Specialisation through perks. Pistols, rifles, shotguns and SMGs could all do with related perks and clearly defined roles. Pistols are low damage/low AP. Shotguns are short ranged/brutal. Energy blow through armour.
People should be able to pick a class of weapons (say energy pistols) and be able to use that exclusively, and pull their weight until endgame.
This ties in with the problem that small has over 30 guns. Energy has less than 15. Big guns has about 10.
Van Buren merged all gun skills into Firearms for a reason.