The problem I find with AA Guns are they are double edged swords. What if your enemy is like me, over her fear of losing fighters to AA Guns? Now she takes all your AA Guns with Germany and Russia’s forced to dedicate tanks instead of fighters out of fear of losing valuable fighters?
Remember, Germany can easily recover from the loss of a fighter, and if she attacks 3 AA Guns with 3 Fighters we’re talking about a 50% chance of losing a fighter (not running the numbers, but 3 shots with a 1 in 6 chance should be 50% give or take.) So each round Germany can count on a 5 IPC loss to AA Fire, but Germany’s earning 40 IPC or more. And, to make matters worse, the Germans can still retreat those planes denying Russia and the Allies a chance to kill them, AND, they can use them as threat to attack enemy shipping still, forcing the allies to concentrate their naval forces.