The shortcoming is the A-20 itself. It's fast, but not agile. It's got a gun that can do good damage (76 L11), but it's slow and inaccurate. The hull armor is 20mm which means that every tank in the game (yes, even tier 1 tanks) can penetrate it with no problems. Its view range is less than 300m so you're likely to be spotted before you spot anyone yourself.... The tank is just no good.