Grens are very good at what they're designed for: being cheap, high damage long-range cover combat infantry. Turning them into another jack-of-all-ranges Volksgrenadier squad isn't the answer.
The problem isn't Grens, it's that Ostheer's mid-close infantry (Panzergrenadiers) aren't fit for purpose.
Yes, you can't compare a versatile unit like grens that have a lot of utility with an AI focused unit like 2bren Tommies.
And the problem with balance is not the grens being weak, the problem is that the Volks are stupidly strong and efficient that looks like that grens are a bad unit.