They were given flame nades because OKW had and still has a hard time against garrisons. They were also given an AI-Upgrade, the MP44, because they weren't a reliable mainline inf past early-game. They were also given the PFaust, due to light tank base rushes. All these changes have been tested thoroughly by the community and finally made it into the live game.
However there are two problems.
Flame Nade: It is being used as a highly effective cover denial tool, an ability they don't need at all. At least not with this lethality. Also, due to the lethal nature and high ROF of MP44s, once an HMG crew catches fire, they get wiped out on retreat.
Do not allow the nade to be used against anything other than garrisons
Veterancy Rate: They also vet up too fast, which cancels the need to build AI specialists or elite call-in inf.
%15-20 increased XP requirement should do the job.
So without messing with their raw stats or veterancy bonuses, or giving cons DP LMGS for example, which is gonna cause troubles; these simple tweaks can make them more balanced against the soviets, especially post-WBP and maxim nerfs.