In the missions for the Carnie contacts in St. Martial my group came into contact with several Master Illusionists, but we didnt farm them. I would estimate about 3-4 spawned per mission with about 6-8 people. Forget what levels we were, though.
Also, the Hammerhead badge (best description ever) is awarded for killing a number of Scrapyarder's minions, but the whole team will get it simultaneously so it might reset everytime you fight him, or is bugged to award to the whole team when one person gets it, I don't know. Hammer Down is for actually doing the most damage to scrapyard.
