I have just joined EBME and was reading a few older discussions. It seems to me that numbers of beds per defib should not be a standard, but rather the time to get the nearest defib to a patient.
In one hospital, we have two defibs 5 metres apart, belonging to different wards.
We have 800 beds, 60 defibs (Codemasters) in our main hospital. I have not worked out times to reach defibs but it would be interesting. Surely that is what matters.