There is more profit in a D3 now than has been in the past 3-4 months. 
Right now your looking at $300+ per month with a single D3 (Of course that is market dependent and can shift at anytime).
Previously I was looking at almost half that.  I think the biggest problem with the D3 is lack of quality control on behalf of Bitmain. I have 4 D3's and only one is a quality miner, another 1 is a problem child and the last two only run on 2/3 boards.