DE Night Shield Question

[Necron_Lord]

In my last game, a Wolf Scout unit outflanked and hit one of my ravagers with night shields with a melta.

The night shields upgrade in the codex states - The vehicle's deck is covered by a broad-spectrum displacement field, enveloping the vehicle in cold and inky darkness. This has the effect of reducing the range by 6". For instance, a unit armed with bolters would be treated as having a range of 18" when firing at a vehicle with a night shield. This adjustment may put the vehicle out of range from an enemy shooting attack, in which case the shooting automatically misses. The extra distance is also counted for working out if the vehicle is in rapid fire range, half range for a melta shot, and so on. Night shields have on effect on template or barrage weapons, as well as weapons with a maximum range of 6" or less. (p. 63)

To use some examples:

Bolter/Astartes Grenade Launcher (Normal 24" range, 12" rapid fire; Firing at vehicle with NS range 18", 6" rapid fire)
Heat Lance/Firepike (Normal 18" range, 9" roll 2d6 for armor pen; firing at vehicle with NS 12" range, 3" roll 2d6 for armor pen)
Fusion pistol (range 6", 3" roll 2d6 for armor pen in all cases)
Multi-melta (Normal 24", 12" roll 2d6 for armor pen; firing at vehicle with NS 18" range, 6" for 2d6 armor pen)

but the next one is the real puzzling one(s):

Meltagun/Fusion Gun (Normal 12" range, 6" roll 2d6 for armor pen; firing at vehicle with NS 6" range, no roll of 2d6 for armor pen?)

RAW - The 6" subtraction applies if the max range is over 6", and the 6" reduction applies to rapid fire and half range for melta shots. Therefore, meltaguns and fusion guns get 6" subtracted from their half range giving them nothing. However, fusion pistols, because its maximum range is shorter, still gets melta.

I gave the melta rule to my opponent to be sporting, but on greater reflection, I don't know if I should have. Do Fire Dragons and drop pod/outflanking marines with meltaguns not get an extra d6 for armor pen against DE vehicles with NS?