good question!

i hardly use D3 with iso > 2500. otherwise high iso noise makes my post process difficult.

for photos I shoot for larger prints ( > 10''), I do not use D3 with iso > 1000. high iso noise seems a lot more ugly and obvious on paper than on screen.

yes, you are right, if the photos were only for screen display, my 28-70/2.8 would probably do the job, with iso = 2500 or larger.