so if miners are not equal, perhaps pools should be segregated? detection and enforcement would need to be worked out, but much more complex systems exist in this world
Not sure what you mean by equal. There is no requirement to use all possible nonces. It doesn't allow them to cheat or gain a disproportionate share of the reward. It is also dynamic. Two different ASIC chips from the same company many not cover the same portion of the nonce range.