If I understand you right, you’d like enemies to rush towards the player from all across the map once a fight breaks, though, on the basis that they should hear the sound of battle no matter how far away they are?
In a terrain size where combat happens, anybody can hear the sound of battle. Sorry for my bad english. Perhaps instead of rush into battle I would mean approach to battle.
I think if enemies see allies going to battle, they can do 2 things, go to battle or flee, not remaining quiet gathering flowers ;D until my party, after dealing with the others, find the isolated enemy.
I ended “Line Battle” scenario right now for the first time, and I think this is the correct way for enemies to approach to battle. All enemies are close to my party, so none is wandering the map scattered. Is nice to see the inteligent AI, with skeleton archers firing arrows from the distance, the damn necromancer raising deads from the distance too, and all the melee enemies fighting. Nice work. With the correct AI, this game will be great.