Increasing the rate of Fire increases DPS in exactly the same way as increasing damage does...its just the time die of the damage over time equation...
yes, on paper... but you have to aim more often
its a difference if you can deal the whole damage in one alpha strike, or have to do it in two volleys.
especially when it comes to railguns,
if that wasn't the case, imperial hammers where the non-plus-ultra in PvP... not just regular rails