I think the biggest issue with mines (captor mines) is that the salvo intercepts the current target in the same impulse. So 40, 50, 100, whatever missiles are all expended in one shot, even if there is only a need for 30 to kill the intruder. Now your mines are expended, and 1 of however many intruders is gone.
Now if the missiles are far enough apart that they form discrete salvos, it should work like you say. Kill 1, move to 2, kill 2, move to 3, etc.