I think they’re all really good, but the design of most of the current PvP maps makes them either a less desirable or an unusable option. In the case of Scout Rifles, Scouts are basically Hand Cannons, except they have high zoom scopes made for long range engagements. There’s only about 3-4 maps were there are lines of sight long enough for Scout Rifles to be viable, and half of them have some sort of side lane(s) that are prominent enough that they hinder the use of Scout Rifles. In terms of the 3 aforementioned archetypes, D2 maps also have a lot of small, tight lanes with a lot of cover and a lot of corners, and not much spacing in between them.
Sidearms could easily become a better counter to Shotguns if there was a little more room in between the walls of a lane. Auto Rifles have very similar TTKs as Hand Cannons, and with bloom being on HCs, Autos have a good chance at beating them. However, Autos need to be able to put of a steady stream of damage to be effective, so popping in and out of cover isn’t a viable option when using them, whereas HC users can simply pop in and out of cover and deal a lot of damage with each shot. Maps with less cover would easily benefit them, with maybe a stability boost to help make their optimal TTK easier to accomplish.
These archetypes, statewise, are really good in PvP, but the short, cover heavy design of most of D2’s maps do not benefit the use of these archetypes.