When u bring in spotter why assume only 1 rifle will face 2 of ur units?Due to slow suppression at long range and bad traverse ,plus ability to gren while suppressed its easy to kill mg even while being in its arc temporarily.Grenadier doesn't have sufficient DPS to halt rifles from flanking ,even if they are out of cover and closing.Closer they get easier it is.
1) Why assume he will have more rifles than your units if rifles are 280 MP and grens and MG42 are 240? If they have teched grenades there should be even less of them as your opponent has invested MP and FU.
2) You can inflict more MP bleed if YOU gren THEM while THEY are suppressed. It is still victory for you in terms of resources.
3) If they are flanking your MG then it is right if you lost it. If not and if, as you said, they are out of cover, then they will get suppressed long before they close in into grenade throwing range. Because of spotter.
It is hard to argue on such theoretic scenarios.
Bring replay where you've encountered such problems, then we'll see.
Without replay I see no point of continuing discussion on that topic.