Chip, Frank and Keith (pluton) - thanks for the further feedback. This is a difficult scene and definitely the most challenging/worst performance by the lens while I had it to work with. Focus should have been on the edge of the blue building in the background, hopefully this is not a misfire. Frank - yes, good things are being said about the Tamron 15-30 mm 2.8, and Tokina makes a number of potential alternatives. The Tokina 11-16 mm 2.8 DX is a brilliant performer on the D7000, so I should definitely take a look at their offerings. Good thing I have time to do this at a leisurely pace, as buying a lens shortly after the D810 would be excessive. Pluton - thanks also for your strong endorsement of the 17-35. I think it is entirely possible that this particular one, a rental, has been handled unkindly in the past. I will keep an eye out for other copies that show up second-hand locally and see if I can make some comparisons.
Cheers again, John