1. I wrote this for the ideal case as if the distance were 1 metre. Then even here you can see the low damage of the machine gun Oppressor.DPS calculations don't mean much in and of themselves, because they assume an ideal scenario that only happens when enemies don't move...though this is admittedly a pretty common thing with NPCs.
All the plasma weapons have serious issues against erratically moving targets because of their projectile velocities, and this is true at ranges way short of 40m. If someone is trying not to get shot, or an opponents path cannot be reliably predicted, for whatever reason, even a twentieth of a second of travel time will seriously impact accuracy.
In my modest experience with them, I actually like the carbines for their hip fire accuracy, which lets me keep my own mobility and situational awareness up. Higher ROF is also more forgiving when it comes to very binary results of damage in EDO's system; any sliver of shield means nothing from that projectile makes it to health/armor and any sliver of health means full and unimpeeded mobility and offensive firepower.
2. 40 meters ? The Oppressor has a range of 35 meters ...
3a. Shooting from the hip can be increased by a mod.
3b. For mobility, there is a special suit mod - movement in combat (with a scope)
4. What is lost visibility from the side ... Here I agree.