Average roll: 2D +6[skill]+1[command centre] ≈ 14, Effect 6, DM on attack AND damage +12...To set up a concentric attack requires an Average (8+) Gunner (capital or turret) check (D3 rounds plus missile flight time, INT)
All missiles receive a DM on their attack roll equal to twice the Effect of the check (positive or negative) and in addition twice the Effect is added to the damage of each missile.
And you can't fail, minimum roll 2 +6[skill]+1[command centre] = 9, Effect 1!
There is no reason to NOT use concentric attack apart from the set-up time, a good gunner basically cannot fail.
Damage increases dramatically:
Nuke missile against armour 15: 6D - 15 ≈ 6 per missile, becomes something like 6D + 12 - 15 ≈ 18 per missile!
This is way too good, at least tone it down to DM = 1 × Effect...