@The Wolf, don't see where your confusion is, so it's probably easier to explain it as a series of choices for ending the LB-X instagib effect.
1: Reduce the modifier for the LB-X versus Light Armour (ASF, VTOL & BA) to such a point where 1 LB-20X no longer instagibs the ASF. Trouble is that the Quad LB-5X Partisan becomes worthless if that happens (it already takes 2 salvos of slow reloading ammo to kill a shiva, if 3 or 4 slow reloading salvos are required then it will nolonger be an effective AA weapon).
2. Increase the ASF armour to avoid instagib by LB-20X. Not a good idea...I can hear the screams from the ASF haters already.

3. Change how the LB-X fires. As I suggest, mirror the Standard ACs, LB-20X firing like a AC20 would still be an excellent brawling weapon but would no longer instagib ASF. The LB-X series would now require some skill to use effectively, right now it's just like MW4 LB-Xs, and that's just a missed opportunity IMO.