I would have guessed that 1.4 and 1.5 would have been more relevant, especially 1.5 since it uses a new memory model.
More importantly, do your charts really indicate anything at all? How can we know what affect the additional CPUs are having when there is no comparison given for a single/dual/quad CPU boxes? This doesn't indicate anything more than "under load, things go slower."
I would also have been interested in seeing how different operating systems might handle memory contention issues.
Your suggestion to scale out doesn't address the possibility that you might need to create shared locks across the network when different nodes are trying to get exclusive resource to something, like a networked cache.
There's also a typo in your chart. The last value in column 1 ought to be 7500.
What is "Service Demand" and how is it measured?