My stock 1080 is getting 20-21mh. I just fired up my old litecoin rig (5 x 280x) that I had stored away in the garage for the last couple of years and that is cranking out 4-4.2mh each which is approx 21Mh in total.

My single 1080 is just as powerful as 5 x 280x which is chewing up 950W of power.. Time to put it back in the garage or sell it off I reckon, what a waste...