Is this the best way for energy efficiency or should there be a different standard?
Though I think what's really missing is a reputable general standard for device control. The master/slave power board thing is a kind of hack using the most primitive kind of signalling we can manage at the moment.
In my ideal world I'd have a control panel somewhere where I could set up rules like "the sound system needs the TV to be on". Maybe the TV could even know that it should turn on the sound system it is connected to, though that's crazy optimistic for the current state of home automation.