AoE spells only affects subjects in the area while they are inside the area (and even new subjects if they enter the area). In this case you want to cast on them specifically as subjects. You could either increase the number of subjects (which requires either a sizeable penalty or a Reach), or you could cast on everyone individually and just relinquish the spells so it doesn't take up spell slots. Less control, but would require individual dispellations if that's something the villain is prone to attempt.