Might be true that an alliance can win that fight, but it doesn't make it "not broken." The fact of the matter is, if you have to run your troops cross country and dump a ton of food to get them there and then truck home with no loot... well, you're going to lose in the long run. It creates a logistical nightmare and gives a huge advantage to the home team that the designers never intended or they wouldn't have included Privateeing in the first place.