[Closed] Shimano brake rotor questions.

Got the new type XT brakes , came with SM RT 75 rotor . I've been using Superstar sintered pads and the result is they seem to have eaten the rotor braking surface . Contacted Superstar and they reckon certain rotors aren't compatible with sintered pads ? Replacing rotor with RT 66 which according to blurb is compatible with metal pads ? Anyone she'd any light on this ? I've never heard of this neither has my mechanic mate . Also new rotor came with thin figure of 8 spacers/washers with 2 holes in , never used these before are they essential ?