When it comes to landscapes the D800E does not lose anything against the D800 - ever. Diffraction affects both equally - and the D800E has a slight sharpness edge. Your issue with the D800E is moire - not sharpness.
As discussed in some other threads, the D800E will likely have a different look with exceptional sharpness of your focus point. Even without any diffraction issues, the sharpness of the D800 and D800E will stand out. It's just the E has a bit more sharpness with the risk of moire. I'll take it and my order is placed. I shoot landscapes, macro and wildlife.
The D800 is a perfectly good option. For a balanced photographer who shoots sport, weddings, and portraits, the D800 is the answer. Anything we are talking about is still the best camera on the market.