This is more of a "feels over reals" kind of explanation, but bear with me. I wanted to show a match wih my modded stats, but Bandicam seems to hate X2 and will crash it without fear or remorse.
It's the start of a new game. It's a wood map. You turn a solider in the chopper and spy a Psyon maybe slightly half a tile away. Perhaps 16 spaces or so. It's in the open. You take aim with a solider, aimed shot, 83% chance to ht. You hit, congrats! That's 26 damage. The Psyon returns fire. It hits, that's 55 damage, instant death. You sigh. You get some more soliders out of the chopper and a few more shots later, the Psyon who killed the first soldier is dead. It's now the alien turn. A Psyon appears. It targets a solider who isn't quite in position. The Psyon hits, does 67 points of damage. That soldier is dead. You grit your teeth. Another Psyon appears. One of your soliders takes an overwatch shot. She misses. The Psyon returns fire. A miss! The Psyon fires again. A hit. that's 59 points of damage. Instant death. At this point, you're ready to cinduct experiments on the terminal velocity of monitors vis. 3rd storey windows.
Early game, every fight with a Psyon can go pear shaped very, very quickly. The impression, and please forgive my language, is that you don't fuck around with Psyons. If I know that I'm fighting Psyons, I'm carrying lots of smoke. I have my lines of exit clear. The third man (I never fght in twos against Psyons if I can help it) is always ready with smoke in case the other two morons manage to mess it up. I would rather spent all my TU and re-position my team to lure a Psyon to me than get into a shooting match with a Psyon, because I know I will loose that fight. That's all thanks to the plasma rifle. You learn to respect it very quickly, and the plasma rifle gives the Psyon character.
Now, same situation. You're facing Sebillians. The Sebillian fires off a burst. One catches the solider. He takes 32 damage. You think "I can handle that". The Sebillian fires off another burst. Another shot hits, that's 25 damage. That's a kill. But it feels different. You feel like the Sebillian has spent a lot of effort trying to kill the solider, that it's been blasting away even though it's actually only spent the same amount of TU and effort that a Psyon does firing the same number of shots. You feel like you can take Sebillians in a shooting war, and you better be able to because Sebillians soak a hella lotta damage, so you have to be able to hold your ground against Sebillians. Shotguns are a vital weapon in the fight against Sebillians, and you need to be able to go over the top to get in close enough to kill a Sebillian. The mag rifle could give the Sebillian as much character as the plasma rifle gives the Psyon, ust based on how it feels to fight them.
Or look at it like this. The mag rifle. As dangerous as the plasma rifle. In the hands of an enemy with 45% more health (100% more health for the Brute) who can regenerate. Seriously? I'd almost rather face Androns. I mean, I notice there are both modifiers for armor penetration and armor destruction in the weapon.json master file. Linear weapons are noted as much for their penetrative capabilities as their power. It's one of the common memes in computer games, that railguns typically can penetrate several enemies at once and/or terrain. Perhaps fiddling with armor penetration/destruction as easy numbers to alter would be of value?
EDIT: For those interested in my edits, I append my currently edited files. You'll have to replace the current files with the edited ones, which means 1) make backups and 2) don't report bugs with edited files, because even though this is just number editing, editing numbers can have unforseen effects in-game. Xenonauts2Mods.zip