See the updated version. Runs about 15-20% slower, which is far less than the difference between single-threaded version and task-based one. Also, it's pretty easy to see in Task manager how all the cores get loaded.
I am having hard time understanding what you are trying to test here. I am worried that .NET code is not really testing what you think it is.
[1] https://msdn.microsoft.com/en-us/library/dd997402(v=vs.110)....
Maybe you mean we should schedule something which has a complete event loop? That would be a lot more fair wrt the Akka version, but the Go version does not create any threads either.