Just to say this was not done to many other action rpg games because they simply don't have the resource to test all the shit player might cause, in the old days kiting a strong field boss to destroy villiage etc is a valid strategy since:
the guard might have unlimited HP/MP
you want to raid the town
And if the game was not designed for it and allow that to happen, game progressing bug might happen and you can no longer finish the game.
That's why Fromsoft's field boss just leave you alone once you escaped the area.