I shouldn't be here, but, this is a subject important to me. So AoE2 ranged units actually have a chance to miss standing targets, alright, didn't know that for sure.
But AoE2 also has something else very, very important, and that is ranged projectiles being able to miss moving targets (projectile lagging?), something that is not possible in AoE3. I tried and nothing. Projectiles are just too fast anyway.
And personally, I absolutely love this AoE2 feature. It indirectly nerfs ranged units and it gives an amazing advantage to skilled players with good micro.
As for making ranged units randomly miss, I disagree with this. This doesn't add diversity and variety... It only makes ranged units less reliable and less competitive (you won't see this is a game like SC2 for example, the most competitive RTS out there).
The less randomization a game has, the more competitive it is. I would personally make all projectiles have 100% accuracy and use the AoE2 system of missing moving targets.
(If by some amazing reason I am wrong and you can make units miss moving targets in AoE3, then please, do tell)