Guess we don't need people complaining about "muh armiger glitch tho" now that I've found this method. I'm sure other people can find an even better way to do it, but for now this is the best I could do. You need to run to the area and have the enemies spawn themselves, that way you can have the large area where enemies will chase you. You also need to kinda stay in the corner so that the enemy circle doesn't get smaller. You can stand in the normal area when using Noiseblaster but after a while the area will shrink. I'm not sure what makes it shrink though so maybe someone can figure that part out.
To kill the last enemy and also escape the area after you get the completed sign, I use the sniper rifle cerberus and stay as close as possible to the edge of the event.