HWguys are the easiest class to beat when scouting.
Get in close, and they'll start shooting, prime a concussion grenade,
straffing from side to side whilst still approaching the HWguy. As soon as
you're within range, let the concussion grenade fly. Most HWguys will not
bother to move away from a grenade - because they have to stop shooting, or
if they do move it will be slowly.  Because you preprimed the grenade, they
will still be got. When concussed, HWguys are crap. They can't use their
gun, due to the concussion effect moving them, and their other weapons are
poor. Circle straffe, or just get in close and nail away. Even thought
they're tough, they won't be damaging you when they're concussed. The only
threat is if another teammate notices you beating up his HWguy!

Regards,
[AnoD]Mephiston