Going back to stealth during the fight shouldn't have as consequence the enemy stops their actions and stays there doing nothing yelling at you. If they have spotted you once, they should move in your direction to look for you. As well, some enemies, like wargs or harpies, should not have a cone of vision but a full circle of detection around them using other senses like sound or smell to find you.
They do sometimes come to look for you. I've seen it happen. But it should happen more I think.
