The control it gives is all that's needed as setting a room temperature back more than 4C will take too long to get back to the "normal" temperature.
really, that depends on your needs. You cannot make those assumptions for all scenarios. That is the reason why there are other types than setback schedule on the market :-)
A 4C setback was chosen because it's sensible for almost all scenarios. We need to compare eggs with eggs, you seem to me to be comparing it to a conventional thermostat ,a Z-Wave one or otherwise that controls the heat source for the home. The wRA+ is NOT a temperature controller of the home, it controls a room or more correctly a radiator. In all applications the wRA+ would also be used with a thermostat Z-Wave or conventional, after all it can't switch the boiler on or off, that's not its job.
Now if we compare eggs for eggs, for Z-Wave you can either fit a wRA+ to control rooms or as you suggest a Z-Wave non-setback thermostat and
a control valve in each room.
However even now do you have control you think you have?
What happens when the house thermostat wants 20C and your bedroom thermostat wants 24C?
The house stat detects 20C and switches off the boiler, but your bedroom stat is at 21C and wants heat, what happens then?
The only way to get this total room control that you want is to have each room thermostat control not only its own room valve, but also control the boiler as well.
For me I'd rather plonk a few wRA+ units around the house and use a setback schedule for each room.
The other advantage is that if your z-wave network goes down these will still control your room temperature.
hu? The other Z-Wave thermostats usuall have local control..