1) In real battles it was common that three or four arrows injure lethally one and the same person. Gunpowder didn't change that at all too.
2) As Crassus said, any enemy, who has more than 0 health in the beginning of the round, is considered to be a possible target until the round ends. In terms of game mechanics, ALL attacks are carried out simultaneously, even though in battle reports the texts are one after another- this is just for a more clear description of the battle. Therefore, no participant can know if his/her opponent will die even if he/she doesn't attack him.
This is the reason why at the end of the round enemies that are (far) below 0 health attack you- ALL attacks are simultaneous.
3) Please clarify what exactly do you refer to as a "problem", so that we don't make wild guesses- it is hard to answer a question you don't know (have you ever read The Hitchhiker's guide to the galaxy?)
