did you ever think that it is in T3 because the buffs it can get on its infantry + doctrine buffs + the effected infantry (tommies with brens + LT) is much higher then what the father land defence can muster with all its buffs including the rest of the doctrine?
HMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMM?
Was about to type this but eh. +1
Don't forget. Volks and Grens don't have SOLDIER armor so with their buffs they become HARDER to kill than grenadiers and volksgrenadiers.