One thing to consider here I think is that Standard Deviation might not be the best measure here.
For example, if you had two courses. One has par 4s of:
250, 270, 290, 310, 330, 350, 370, 390, 410, 430, 450, and 470. The other has:
250, 250, 250, 250, 250, 250, 450, 450, 450, 450, 450, and 450.
The standard deviation of the first course is about 69, while the second is 100. I think most would agree that the first one offers more variation though.