Okay, so I luckily discovered a website were the stats of all weapons currently available in game are displayed, so I decided to calculate the DPS (damage per second) of all weapons available but melee weapons. I think it may give clear ideas to everyone.
SMG :
Hochfir-SMG : 121.65
SMG-9 : 123.8
Blishlok : 124.5
KEK-10 : 128.33
Crotzni : 130
Crotzni earns it’s state of most powerful SMG, while Hochfir-SMG is the weakest. however everything seems pretty balanced among SMGs. Between the least powerful and the most powerful one, you have only a gap of 8.35 damage, which is pretty negligible in my opinion. In short, the best SMG will be more likely to be the one you’re the most fond of.
Assault rifles and machine guns :
M4A1 : 125.07
Timik 47 : 128.33
Stark AR : 131.25
BR-16 : 131.25
K-121 : 134.87
Dreiss AR : 150
Dreiss AR feels clearly superior with more than 15 damage above everyone else, but the gun is not seen as the most easy to use. Everything else feels more balanced around 130 DPS. I was surprised to see that the M4A1 is the least powerful of them, only slightly more powerful than the Blishlok, but since the M4A1 feels kinda accurate, it’s not such a problem.
Sniper rifles :
FEL-IX : 49.375
MoA SNPR-1 : 53.75
PDP-70 : 150
Do not let the numbers abuse yourself here ! Yes, PDP-70 have and insane DPS compared to the two other ones, but is also much less effective ammo wise. PDP-70 will only deal around 45 damage per shot, and won’t one shot anything above 90 health, while every other snipers are much more likely to be one shot one kill.
Shotguns :
Hollunds 880 : 126.13
Remburg 7 : 137.6
Remburg 7 is more poweful, but has one less buckshot in clip. Also the Remburg 7 can one shot Proxy. I may be tempted to say that this may make the Remburg more interesting than the Hollunds 880. Balance between shotguns may need to be looked at.
Machine Pistols :
Tolen MP : 109.8
MP-400 : 115.86
MP-400 may be slightly more efficient than the Tolen MP. Tolen MP has 5 more ammo in clip, but this may not be a good enough reason to use it instead of the MP-400. This may need to be looked at.
Pistols :
M9 : 112.5
Selbstadt .40 : 112.5
Caulden : 114
DE .50 : 120
Simeon .357 : 125
Smjüth & Whetsman : 135
You want to hear something funny ? Smjüth & Whetsman is the third most powerful weapon in the game DPS wise (without counting reloading of course). This said, the non-auto secondaries follows a sure pattern : more ammo = less DPS. Caulden may need to be slighly buffed though, while Smjüth & Whetsman may need a slight nerf IMO (just to get a bit more around 130).
Conclusion ? TTK in this game is SHORT ! Most of weapons will shred a 120 hp character in less than one second. And even less than half a second if you are an headshot machine. I must say that I kinda hoped for a slower TTK, but this is not the subject.
Those informations are not enough to tell if a weapon if balanced or not, since we lack some informations like precision or reload time. We can however have a small idea of balance by looking at the weapons in game. Huge DPS weapons like PDP and Dreiss AR are compensated by big recoil or lack of ammo. Secondary weapons feels less balanced between : most of people will be much more tempted to use a machine pistol over the M9, the Selbstadt .40, the DE .50 or the Caulden, since machine pistol have a huge clip and a close enough DPS. Overall however, DPS is not enough to know if something is clean or not.
Here is where I got all the necessary information to calculate everything : dirtybomb.gamepedia.com/Weapons
I calculated DPS with the following formula :
(RPM / 60) * Damage per bullet = DPS
That’s all, I hope this will be useful for everyone. 
EDIT : okay, I’m stupid. I calculated everything while it was already available on the link above. Derp.