And yeah, a legged 'Mech is pretty much doomed. What's the point again?
He doesn't really have one. The point is that a 'Mech is able to continue operating in that condition and a HERC is not.
Only if your definition of "operating" is equal to trashing on the ground.
Well, technicly, a war machine is still operation as long as it can fire. If one of your weapons is still functional and you can wiggle the mech a bit, then I'd guess it will still be "operational".
A HERC doesn't have a rotating torso, but it's weapons can track and swiwel, so a Mech would be somewhat better at trashing around until it faces an opponent.
Either way, sucks for the both of them.