It is not question of realism. Don't get me wrong, i have no desire to see german ubermensch terminators fighting hordes of russians armed only with sapper shovels, but gameplay>realism for the sake of the game. Losing pak entirely to volley of ptrs shots as bad as losing clumped 2-3 man squad on retreat to marksman volksgren with his trusty rocket launcher which made to destroy tanks, but, apparently, kills infantry better than rifle. Both situations extreme examples of bad game design.
This. Every time someone says unit X is OP/UP, other factions' fanboys start saying "What about Y? Why what unit is blahblahblah". We can go on and on and justify balance issues by comparing OP/UP units and weapons.
AT weapons sniping infantry are bad design, no matter if it's Panzerschreck or PTRS. Although, PTRS should have AI capabilities when it's used by Guards or partizans. But a change like this on you main line infantry is bad. Take a look at OKW. Why we are frustrated by SchreckBlob? Because you turn you AI core unit into laser guided tank hunters. Any drastic change to mainline infantry has the potential to break the game, because they are spammable and cheap.