Maxim is not a super survival as many here claim. That case which I described above happens all the time. If we compare the Soviet mortar against MG-42 and the German mortar against Maxim. In most cases, the German mortar will win, and that is with 6 people.
Mortars are intended to counter HMGs, and the Ostheer mortar is intended be slightly better than the Allied counterparts because Ostheer is based around strong support weapons.
What does this have to do riflenades and your claim that supposedly they can be fired against a Maxim in a frontal charge and can wipe out 6 men in one hit? "It happens all the time" is not a valid argument when the stats indicate it shouldn't be the case, unless you can provide us with a bunch of replays that prove otherwise.
It is a stone cold fact that 6 models with the same model HP (80) as the models from a 4 men crew is more survivable against the same type of weapons, in this case grenades, as long as they aren't all bunched up in yellow cover (which again, is in the majority of cases a player micro error).