T-70 cost efficient unit? Yes and we see it in games.
T-34/76? Yes, we see it in games.
SU-76? How often you see it in games? After rework of ostwind it become more playable unit in games. After rework of SU-76. Where it is?
While combo p2+puma i see very often. I don't see in any high-level gaming strat t-70+SU-76. Or intentional su-76 production. Even as "AT of last chance" it don't work.
The argument that a unit is not being used that is not cost efficient does not hold much water. It was proven clearly by Dshk or even shock before the buff.
Luch needs a Puma since it extremely low AT, T-70 does not need a SU-76 to protect it.
I have provided you the stats that SU-76 is superior vs mediums tanks to Puma.
While other rare SU units - mortar and M5 have very narrow role and do they job. Give smoke and AI against teamweapons and AA against planes. SU-76 don't have any roles that SU don't already fill. AT against LV? PTRS penals or zis with cons at nades. AT against mediums? Zis. Barrage against teamweapons? Zis. With this patch and reduced cost of T2 - zis will be much more reliable choice neither su-76.
And that is why lowering the price of T2 for soviets makes little sense, it did not help make t2 built more attractive it help to back tech and making a zis instead of SU-76.
Once more the main reasons you do not see units like SU-76, Easy8, Sherman 76, 105 dozer, Panzer J is not that the units are somehow bad:
there are simply better options to invest resources in
Ostheer have little reason to invest in T3 units