Having used red dots in competition and made shots out to 400 yards on 4moa targets, it simply takes practice.
I agree and think people get caught up on dot size, thinking they can't shoot small groups or small targets with a dot over a certain size. You just have to use the dot size to your advantage. For targets, you need one that you can consistently bracket the dot against. For critters, you can use different parts of the dot, not just "the dot".
