[X] Have the landing zone be just outside the outer walls, 15-30 km from the AA. - This will allow your forces to receive the resupply almost immediately and make it trivial to prevent harassment but the lander will suffer heavy losses from Dark Eldar AA. Another advantage is that your AA will be able to provide covering fire reducing the impact that Dark Eldar fighters can have. - Will suffer heavy losses from AA and reduced losses from fighters, best taken with suppressive fire artillery choice.
Best choice, no harassment, less fighter losses, counter the AA with suppression fire.
[X] No escort (outside walls option chosen).
[X] Concentrate fire on one target.- This will allow your artillery to have a major impact on the selected target at the expense of have no effect on the other targets.
[X] Suppressive fire- When the Dark Eldar AA opens fire have all artillery target their locations, or your best estimate of their locations in a bid to reduce the volume and accuracy of the Dark Eldar AA and reduce the amount of losses that your air force will suffer.