In the city map, I had the same problem.2 Artillery were nailing the Tiberium Refinery.
We had the refinery down to one health bar, then suddenly my partner chooses to shoot at Soldiers trying to distract us (soldiers can't do squat).
The refinery was being repaired by engineers and they were repairing more than I could damage. This went on for about 30 seconds and my partner is trying to nail individual soldiers running around the GDI base.
We could have easily destroyed the refinery had my partner listened to me and kept hitting the facotry instead of toying with the Soldiers.
I was eventually destroyed, he ran away, and the GDI refinery was fully restored.
We never had that chance again because after that Mammoths came out and destroyed us.
[ March 04, 2002: Message edited by: eg ]