Warren's being really dead or only momentarily dead enough to let the First take his form has exactly ZERO impact on how I look at ANYTHING. I agree that on a technical level, it was a mistake. I just don't see how it's a mistake that impacts the storytelling in a material way. I expect Joss to pooch details about the technicalities of how the 'verse works. I don't expect him to pooch details that matter to the emotional/thematic content of the stories he's telling.