We are developing real action-based combat system, where aiming is not a mere 'lock on target'. It will be possible to miss your target, and your enemy will have the chance to avoid your incoming attack, by moving out of the way. Naturally, you can swing your weapon or shoot your arrow into ground or a tree, no automatic-target locking will be possible.
Your aiming skills will affect not just the chance to hit or miss your target, it will also affect damage bonuses, depending on where you hit the target. Your character stats will further affect your chances of such additional damage.
For example, a head-shot will have very high chance to do critical damage and cripple your foe.
Sneaking up on someone and firing from a great distance, to miss, will already alert the enemy by hitting the nearby wall or a tree, or the sound of the arrow flying.