While I agree with the general idea of what OP is saying (insane vet is insane), it's really only terrible when playing as Ost. Grens get brutally outscaled, to the point where they become incredibly hard to use.
Just look at the stats:
Grens: 4 man squad, 240/30mp, 1 purchasable upgrade slot (Long AI)
Rifles: 5 man squad, 280/28mp, 2 purchasable slots (AT, Close AI, Long AI)
Infantry Section: 4-5 man squad, 280/28mp, iirc 2 purchasable slots (AT, Long AI)
Conscripts: 6 man squad, 240/20mp, 2-3 purchasable slots (3x PPSH, 2x PTRS)
Early game, yea, their survivability isn't an issue do to very high long-range DPS (except vs. tommies), but by late game, they're insanely weak. Losing ONE model cuts DPS by 25% (vs. 20 to 17% for everyone else), they can only buy one upgrade (and pick up a second one) vs. everyone else being able to buy 2-3 and their upgrade is ONLY good vs. Infantry at LONG range (vs. AT, Close, medium and long AI).
Add to that the AI's tendency to group up making the 4 models much more likely to take heavy losses to AoE (in terms of squad %), resulting in a quicker retreat (less models to lose), and a higher reinforce (why!?), they end up getting pushed around a LOT by late game.
Seriously; try it. Get a vet 3 1x LMG gren squad in yellow vs. a Vet 3 2x BAR or M1918 rifle squad in yellow and see what happens. MP cost they are 7.7% more expensive per model in initial cost AND reinforce per model; but they'll lose every single time (the base cost on rifles gets you an extra model and thus more HP).
However, IMO, the solution isn't to nerf vet (although some of it needs to be looked at). Instead, gives Grens a "bolster squad" upgrade that simply gives them +1 model, and +1 purchasable upgrade slot (so I can buy a 2nd LMG).
You'd be right if Ost didn't had access to best HMG in game and sniper.
But they do, no one in his right mind spams grens vs rifles, because thats about the worst thing you can do. Rifles hardcounter grens, not the other way around.
Ost have way more tools at any time then other any allied faction, USF have rifles exclusively at early game. Obviously rifles will beat grens at all stages, that is their intended role and balance.
You can't have wide selection of supporting units AND mainline infantry as strong as opponent, when opponent have ONLY that infantry to pay with.