Maybe different batches, but my WDC 2TB black ran hot with no negative side effects(but It had very little fresh air).http://www.wdc.com/en/products/products.aspx?id=760
Operating -0° C to 60° C
Non-operating -40° C to 70° C
I am not sure if one just had more air flow, but I do not think you have to worry.
On the other hand, my old WDC Black 640 ran very cool and much more quiet then the new one.