It is true that the number of cores do not matter as Revit is generally running single threaded.
There are some performance bottlenecks when creating Revit elements, like family definitions or 1000s of Directshapes. Using data dams, disabling slow components or using a trigger to isolate slow components can help alot.
There is one area of performance you can see if it shows things down, that is the previews. Turn off the preview on the rhino toolbar on Revit. Does that help? I saw something similar the other day that 27,000+ elements in the preview slowed everything down. This is something we might be able to improve.