You've left out penetration in your comparison, which is decisively in favour of the Panzerschreck at 160 vs 110 at max range for Bazookas and PIATs. Guaranteed penetration against any Allied medium vs a 61-47% chance to pen a Panzer IV.
Ones pays more fuel for the extra armor and hand held AT weapon do deflection damage regardless.
Given the cost difference between PG and RE/Ro.E imo the later are quite more cost efficient.
When compared with Ranger/Paras with a similar cost they could far less effective.
Scatter/collision hits are almost non existent on handheld AT with the huge scatter values on Bazookas and Schrecks (16 scatter angle and 15 distance max) while PIATs have very slow projectiles (when they don't track on a hit-roll they will likely miss if the vehicle is moving).
I am not sure the claim is accurate.
1) Scatter distance max is the upper and thus it is not very informative.In addition high scatter distance max is not necessarily a bad thing, combined with distance offset make the projectile travel further way and thus actually increase the chance of collision hits on retreating vehicle.
2) Max values might be higher but on the other hand ratio is lower than other AT weapon which means that the weapon scatters less with distance.
3) The problem has more to do with scatter angle but even then its more 50/50 if the vehicle is moving perpendicular
In terms of cost efficiency, Panzergrenadiers and Panzerfusiliers also have better veterancy bonuses with +40% accuracy compared to +20% for RET, +25% for Rangers/Paras and +0% for REs. The latter do get -50% reload in cover but that's not of too much use when chasing tanks.
So still with these changes I would not consider Panzerschrecks to become any less cost efficient than they currently are.
They also have higher vet requirement while accuracy bonus for RET comes at vet 1.
As For USF elites they can stay on the battlefield much longer.