The armor is paper thin, and light mechs (even some heavier ones too) go faster. Harasser is supposed to go 162kph, which would give it a touch more survivability, and the ability to actually catch up with mechs. I know MWLL isn't following the TROs exactly, but in this case, I think adjusting the speed to more closely match it makes sense. Hovers are supposed to be annoying little speed demons, not Partisans with half the armor.