I still don't know where people got this idea that Nas/Jay-Z songs don't work. They don't even have that many (that were released). And the first two they did ("Black Republican," "Success") were great.
I do agree that they shouldn't treat it like a grand event every time they collaborate, but it's also not something they do all the time so expectations will always be high. Imagine Michael and Prince getting together. The song will never be as good as what people want, because if it isn't what they want, it's automatically trash regardless of how good the finished product is.