I would say Mission 4 would be poor concept and execution. First of all, the enemy would not hunt down player automatically. There is really no reason to hunt down all zombies to begin with the storyline. If there is a map highlighting all enemy or showing number of enemy left, the play experience would be much much better.
Mission 3 was a pain too when returning back to the manhole from the mansion. The "open world" is so huge with no map highlight. I usually spent more than an hour to find my way back to the manhole. With the map of this size, it is really necessary to include a map. It is funny if player know the way it would be less than 5 minutes to make it to mansion, but took way way long time if player is lost in the forest.
Mission 3 was a pain too when returning back to the manhole from the mansion. The "open world" is so huge with no map highlight. I usually spent more than an hour to find my way back to the manhole. With the map of this size, it is really necessary to include a map. It is funny if player know the way it would be less than 5 minutes to make it to mansion, but took way way long time if player is lost in the forest.