Nikon 50/1.8G vs 60/2.8G at small apertures (for landscapes)

You mention the Samyang 14/2.8 and Sigma 150/2.8OS.

FWIW, I have the the Rokinon 14/2.8 and this is the only of my lenses I find disappointing on the D800. The center is never really crisp at infinity and corners/edges are simply bad, even stopped down. Maybe I have a bad copy. I also had the Sigma 150/2.8OS. Contrast detect autofocus in live view didn't work with the D800 and I returned it.