Atreides have to be one of the strongest defenders, with the Machine Gun Tower and the Missle Turret. It is simple to defend with simple Infantry, First find the entrance. If possible find the main one. Build 10 Kindjal Units and 10 Snipers. Place 5 Kindjal and 5 Snipers on either side of the entrance. Deploy the Kindjal and bingo, you've got the kindjal to take out tanks and the snipers to take out infantry.