Hard to tell in some of these images where the focal point would be. Also looks like you used a large aperture for shallow depth of field, that makes judging focus a little more difficult with this set.
I just did a shoot with a D800 + 50 f1.8G this afternoon (ok, it was just my kids!) but I was very happy with that combo. Used it mostly at f1.8-5.6 and sharpness was not an issue.
|I am an Elephant by Bibix|
from An A to Z of Subjects- Week 5, E
|Mossy forest panorama by Jill Hancock|
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|Ship Moon and Stars by LJJohnston|
from For creative newbies only..