If you'd like to speak about this matter through private, my skype is always open.
I still believe that a bunch of people who seem to be thinking one thing, or are 'always' in a state of distress as they cannot control their body would still bring up a few curiosity flags.
All one would need to do, is capture one, force their way into the head and figure out the reasoning for such distress. The Nomads would be the ones to rip apart a human being to figure out why it's doing that. There 'have' been a few specific ones that come to mind that would do this without a second thought.
If a human is not acting or thinking like a standard person, it'll be investigated eventually. Sure, there are plenty of crazies out there however.
There isn't many ways to be completely Nomad-invisible. The nomads know a thing or two about the Humans as well that they think the Nomads don't. (Granted the Nomads don't know 'everything'. Humans are a difficult bunch. They do have their own secrets admittedly, a large amount of 'em I suppose. it would be impossible to know 'everything'.)
Of course, things cannot be acted on as Humans greatly outnumber the Nomads, and casulties would be insane. Thus the lack of full-scale war. The Etherium are a different story.
I do appreciate the short explanation on how it would work, I would love to hear more about their capabilities and the workings behind them. That's always been something I have been interested in. Factions of all sorts. A new species? Even better.