There is really no point randomising at all, any cycles you spend on it are a total waste - one of the most important properties of a good hash algorithm is tha

There is really no point randomising at all, any cycles you spend on it are a total waste - one of the most important properties of a good hash algorithm is that a one bit change in the input should result in an output that's completely unrelated to the previous. Your random number generator is pretty much equivalent to feeding a counter into SHA256, so using it as input is pretty much equivalent to hashing a counter twice. There's no point!