Cruiser AA defense is too powerful

Cruisers have a lot of AA, consider the fact they are loaded with multiple AA guns of varying sizes depending on the ship. Lets consider the lvl.6 German cruiser (13 air defence) Hipper class, it had 12 37mm guns, 8 20mm guns and assorted machine guns all mainly used of AA. Also some of the heavier guns such as the 12 105mm guns could be used as flak if they have the firing angle to fire up. Now the German lvl 5 AA (8 air defence) is only a 128 mm flak. But also AA is cheaper than a cruiser and cruisers only operate on the seas, most battles occur on land.

Cruiser AA stat is in fact 6 at level 1, and is quite representative of the fact that the Cruiser does cost five times as much iron and goods, and half as much manpower as the AA gun does.