NC MAXs do have a mid range weapon: Slugs.
Also, sniping just takes practice.
My favorite inf. loadout is:
SAS-R
-Suppressor
-3.4 Aim-point
NC 6 Mag Shot
-Suppressor
-Flashlight
The SAS-R can one hit KO enemies in CQC with a headshot and if you miss just whip out the Mag Shot and spam. With a bit of experience you still learn the bullet drop and still snipe. Use the Mag Shot or Desperado since the Rebel and revolvers aren't fit for spamming. Also the flashlight should be used on all sidearms to deal with stalker cloaks.
Until the straight pull bolt attachment is added to live servers, I would suggest putting the flashlight on the SAS-R as no other attachment for that slot does anything useful for it. Once the straight pull attachment is in, that might change depending on what slot it goes in.
I use the same loadout as my slot 1 infiltrator loadout except I use the flashlight on the SAS-R and a Rebel in the pistol slot, with a suppressor and laser sight.
I mean when there's two liberators daltoning your spawn room and you can only hope to survive by running outside like an infiltrator.
You can't pull vehicles or MAXes then... :/
If you don't have it, save certs up for the HA AA launcher. If you use it with a few other people libs will have to leave to repair, especially if you use the launcher in conjunction with other forms of AA that can keep hitting them past the launcher's range.
I don't think spawn room warriors should get crap like they do. If leaving the spawn room results in instant death all you're doing is feeding the other side certs. It's much better to just sit inside and do the same for your team as people run past the doors. Plus you can lay down an ammo pack and hit the xp cap for it really fast, or play medic and rez the poor fellows who decide not to be a 'spawn room warrior.'
Unless your side builds a max crash or at least forms up to run towards the nearest point at close to 50/50 pop, just stay inside and make you some certs.
Either that or go to the next base down the line and set up mines if no forward enemy vehicles are there.