I have been trying to gather all parts for a set of three devices. The base devices should be easily obtained from CoH or from friends/trading. Then the parts from SL. Since I currently have an active SL-account I logged my highest level character, an agent who has the garden keys and kills any boss at this level in a couple of seconds. I found Shere Map
with locations of all the named mobs. I started rotating between 3-4 different camps to time the 20 minute spawns: named Imps, Hiathlins, and the two Dredges.
A couple of hundred Imps later I had three Focus Funneling Spirits. At that point I had also found two Spirit Training Program (love).
Now focusing on the two Sadistic Soul Dredge. Like others have reported, they seem to be the real issue. After a few long gaming sessions I've found nothing and I'm afraid that I might delete the item once it finally drops. If it drops. To ease the pain I'm also killing named Souls (for NCU-upgrades: Problem Seeking/Avoiding/Solving Device) as well as the named Heartland Predators (for Predator Armor).
Right now I'm counting 4 complete sets of Predator Armor and 32 Problem X Devices. After assembling 100+ Complete Blueprints I've stopped looting Patterns. For some reason I've also gathered a set of shade spirits/tattoos, 9 Die Kleine Nadel (QL63-143), a couple of Elysian Protector's Cuirass, and Novictum that I keep deleting...
I haven't seen any other players at the locations for Imps or Hiathlins. I've seen a couple of players farming Souls on the island near South of Elysium but noone camping the Sadistic Soul Dredge there. Maybe because he is often hard to target and sometimes invisible. The only mob that other players seem to camp during weekends is the Sadistic Soul Dredge in East of Elysium. Perhaps they are also struggling to find the last piece?
I'll post an update if/when I've completed this mess.