No, ofc. not. No MG should be able to hold a sector on its own. The MG42 is close to it, but fortunately not quite a no-brainer.
I'm used to deploying MGs as back up for infantry. It works fine for the other factions for example to soft retreat infantry and draw the enemy infantry into the arch of fire of an MG waiting behind. Then when they get supressed, counter with own infantry. The problem with the 50 cal is that it loses half the squad before it can supress much. So in many cases, the position still gets overrun.
Come to think of it, the 50 cal seems to work pretty much as the soviet dishka (minus the AP). If the soviets didn't have any other MG, they'd also be screwed.
And finally, it's ironical that one of the info texts on the loading screen is about how the 50 cal is effective against vehicles with its AP rounds.
Here's a replay where OKW had the perfect little sim-city to use it on, 2nd barrage gets some nice hits.
Nice replay. It seems like you get about 5 volleys per strike? (hard to be sure because they are so scattered that the area is wider than a screen). I wonder why I haven't had that work so far.