Basically, I'm pretty sure, you're not getting a clear picture, if there's are more than one device on one measurment device. There's too much noise to be considered and the logic would be a total mess. I didn't expect much from my 10€ China-device, but it seems pretty stable. If you have a dedicated measuring device of any kind, you have to find out two things:
1. how is the power consumption regarding to what you would like to achieve
2. how short your intervals schould be. I can imagine a toaster requires a much shorter interval than a washing machine.
If you have done this (like @ThomDietrich explained in the first post of this thread), you can then adjust your rule to that.
Long Story short: I don't think there's a device small enough to be monitored and it is nearly impossible to filter a specific device, if you connect more than one to your power measurement device.
as explained above, the 10€ China-device delivers enough output for a clear rule. I don't know the Aeotec HEM, but it should do the job. All you need is a reading of the wattage over time and then compare it to your thresholds - that's it.