It really worries me how much people are focusing on how they want to be able to play only on the Gamepad. If that is the feedback that gets to Nintendo and developers, they're going to take it to heart, and it would really be a negative thing for the system. Wii U is not a handheld. Why do you want it to be one?
ZombiU in particular shows how awesome the things possible can be with the second screen experience. If that second screen just becomes a copy of the main screen, it takes away the whole thing that makes this system unique and instead turns it into a handheld.