I hear ya, but I've got the legend referenced in two locations on the drawing.
It's not too big a deal anyway...it just makes it easier for them if someone wants to isolate different parts of the drawing.
What it is is a Data Highway network, which in essence, is similar to a pipeline. We've got the main trunk cable going horizontally from one side of the drawing to t'other. These trunk cables are of varying colours and linetypes (controlled by the layer "Com-DHPlus", "Com-Ethernet", etc). All of the devices are connected to the trunks via drop lines. Devices are placed on layers like "Device-PC", "Device-PLC", etc. Sounds simple enough, but if someone wants only to see the PC's, normally, we'd freeze the other "Device-*" layers. Since we don't want to see the drop lines just dangling out there in the middle of nowhere, I've set up these drawings so that the drop lines are placed on the same layer as the device it's connected to, then the colour and linetype is changed to match the properties on the main trunk line. So, when a device layer is frozen, everything disappears up to the trunk.
If that makes sense to you, great...It's kinda tough to explain, but once you see it, I think you'd agree.
Cheers,
Mike