You expect a 260mp unit to completely negate 280mp + 280mp + 280mp + upgrades + vet3 units?
The MG's role is to suppress/pin infantry in front of it. That means, yes, if you run 3x vet 3 squads right into it, all together (i.e. not even attempting to spread them out), they should all get pinned pretty quickly.
Split your army, use smoke, flank, etc. A-move should not be viable. And yes, this should apply to all MGs/teams.