This level lacks is in how the Simulants react to the stairways. A lot of the time they might not even come up or down to get you if you sit and wait in one spot, you have to move around (more than just in your level) to get them to come to you. However, if you stay on the top level and move around (even in a stairway once in a while) that the simulants most likely will show up one by one. If you move around in the mid level you may have more simulant activity. You could also send one of your team members out to run up and down the stairways getting the attention of the simulants and drawing them to your base area. Teams that are attacking another team will have work to together to overcome their opponents.