Guards prioritize attacking far away weak hostile creatures rather than current target
Different from how vanilla does it. If a guard is already engaged in combat with an NPC or player, he should not change targets unless the other combat target is closer to him.
To test:
Order a guard to attack an npc Then spawn a rat some distance away
Openmw: The guard will chase the rat
Morrowind: the guard ignores the rat and tries to finish off his current target.