I'm new please help w my loadout

Sniper rifle and buckshot shotguns are the only two weapons where this context matters, though I see your point seeing how this is a sniper thread.

Slug shotguns aren't competitive at range either, they're just less crappy than buckshots beyond point blank range. Inquisitor's effective range is much better than of any slug shotgun's. Same applies to SMG's apart from the PDW.

I can also imagine a Heavy Assault with a non CQC LMG (or an MCG) making good use of a high DPM secondary. With 4+ second reload times, you can't always simply run around the corner and reload. If you have an Inquisitor, you have a fighting chance against two non-heavies in a row, while other pistols would be more likely to run dry before killing the second guy.