Grenadiers counter m3 or wc51 pretty well seriously unless you spread too much and/or don't use cover. Faust range is enormous so they cant come close at all and grenadiers long range is pretty good so it deals decent dmg to the vehicule even when it s far. Think also that making those means your opponent has less capping power so it s not as important if you dont spread as much and cap slower + in team games you don't even need to spread anyway since you are just in charge of few teritories.
Someone also suggested that it may be problematic if they all go on one player but that has always been the case with every unit and it just means you'll cap the rest of the map without facing opposition. In that case just retreat your squads faster then you would normally do since they can chase and regroup with the player(s) that would be their normally their next target. Blobs own scout cars. Massing them in team game will only win against bad players.
Btw, you really rarely see any soviet go scout car against wermatch because grenadier is such a hard counter
Grenadiers cannot do decent dmg to wc51 using rifles... Try to do this yourself, then you will know it. The wc51's armor is not like kubalwagon. And when you wanna faust it, well-mirco player will kite your Grens to death. Using cover was my first thing to do when I saw the wc51, I put the Grens into a building, but the wc51 carring a RM squard can still do decent dmg to my Genadier, as you know, the Grenadier has only 4 members. Then when I retreated this squard, he wiped out my Grenadier. Yes you can hold a defensive position with 2-3 Grenadiers together to avoid facing wc51 alone but left the territories captured safely by the enemies one by one.
Well perhaps the real problem is not the wc51. It is the 3CP M3HT with a flaming Assault Engineer, also a fast-tech Captain which has Bazooka will join. All the Ostheer players will build 222s to counter the wc51 when they see wc51s spam. Then they obviously lost the battle to M3HT carring a Captain... The 222 is too too late to counter early light vehicle spam. They suck when they come out at 5 min.
I have faced this only once. I think the 4 guys were in a team. Their team worked pretty well. They know the weakness of Ostheer. And very unluckly we have a 4 Ost players random team...