If you choose to hang around, an uruk captain will come over to investigate the commotion and that's where you're in trouble. From a distance the captains look like any other uruk. You need to scour the battlefield before you jump in - figure out who the captains are, where the explosive barrels are and how you're going to lure one towards the other.
Fortunately, uruk have pretty bad eyesight and aren't willing to climb. If you need to escape, you rarely need to do more than scurry up the nearest wall and hide on a rooftop until they get bored.