Yeah, they should trip at much much less than 30mA. 5mA seems about right.
When I lived in the US, my house had them in the bathroom, in the kitchen, in the garage, and outdoors. Each single RCD/GFI device controlled a downstream daisy chain of about 3-4 ordinary sockets.
I'm in Canada now, and surprisingly there is not much in this current home. I actually put them in myself here at the kitchen and bathroom, and one on my bench. This house is older though, about 1970's so it's probably understandable.