imo, pistols should be underpowered. The weapons that heavies have should be better than light weapons. The pistol shouldnt be able to compete with a minigun, it just doesnt make sense. Weapons should only be balanced within the category that they're in.
I'd argue that light weapons should be high damage dealers to compensate for a lack of health, not 1 hit kills or anything, but enough to have a chance in combat, maybe not pistols but rifles and the such.
Of course the heavies will have access to these weapons as well, but I'd think the heavies would focus on high ROF and fill the air with lead, while lights did more damage per shot but had far less ROF, and the heavy would win in head on bouts but if the light is good enough he can use his agility to help him win.