If the accuracy of my rifle and ammo, matches the MOA width of the red dot I am using, and my zero is perfect. Then the red dot is basically my possible impact zone. This is true even when magnified.

Is this a desirable thing, when shooting at combatants at say 400yards? Or is it not really a benefit, because wind will probably always erase that effect.

- obviously asking for legal purposes only.

*Lets say this is, using a modern combat carbine, a 2 moa accurate 556 AR.

I think the smallest dot that your eye can read quickly at a moderate brightness is preferred. For me about 3-4 MOA, which is handy as a BDC. Top of dot 100, center mass 200, bottom of dot (4:30 or 7:30 with wind) 300yds.