I like the ability to stop one person from running past you. I also dislike that the rules let you be absorbed in dueling one person, then freely smack someone else who happens to run behind you.
So, what if we just had a rule like, "If a hostile creature enters a space adjacent to you, and it is the only enemy adjacent to you, you can choose to stop its movement."
Basically, you can run up to someone and attack. And if you're fighting and you want to run away, you can do that too. And if one of your buddies is distracting an enemy, you can run past without concern. But if the enemy isn't currently engaged with anyone else, you can't run past it unless it lets you.