Well...at least we have better graphics?
Seriously, I don't know that this was a completely accurate portrayal of the combat, but I see your point. While this probably wasn't how a battle was intended to be fought in the games, that is an actual tactic. (Real-life method incoming) As you run away, the fastest attacker splits from the others as they compete to catch you. You turn and beat them, then run until the next attacker splits from the pack. This is repeated until all attackers are down and you win, or you tire out and lose. This, of course, relies on the defender being faster than the attackers. If you are slower than them, they will just tackle you and beat you to a pulp.
Moving on: There is always going to be a limit to the AI's tactical abilities. In their programmed minds, they number more than you so they should have the advantage if they attack. The AI doesn't understand the concept of their target purposefully running away on foot to attack them in this way. The intelligent thing to do? Have them run for a certain distance, then give up and return to the archers in order to force you to confront them from well within their projectile range while defending their archers from melee attacks. The archers should not be constantly moving as they are shown to be doing. I mean, they have shields! make a shield wall and soak up the arrows! But AI is not that intelligent and just assumes a win from numerical superiority. Could they write code to account for this? Yes. could they write code to account for every possible tactical maneuver and be able to have the AI process all of it and apply it in real-time, including adjusting for counter-tactics? Not within the constraints of current technology. Maybe once quantum computing is available to the masses, but it would take decades, possibly centuries to program. In other words, it should be available in Mount & Blade 3: Tribal Ascension (since they seem to be going backward in the timeline).
I both excitedly wait for and fear the day when AI tactical intelligence can outsmart a human in real-time. That to me will be the beginning of the end, but games like this will be so very realistic so it won't be all bad...