A USSR being in Berlin in 1942 does not belong to that. Nor will it be that way in the final version I'm sure, as this AAR is based on an months old beta.
Exact representation; probably impossible as when you would replay history now with all the real persons again, the outcome would be very different, it's called hindsight. But, every nation building huge tankarmies to go on conquest sprees should not be possible, neither does a USSR holding Germany back almost on the border. when HOI1 came out, there was NO eastern front, the USSR AI was totally unable to do anything, so you didn't even need to prepare, that changed a bit later a lot already after the first few patches. We are all trying to push as hard as possible here to get as much balance in PRE-patch, or at least point it out, as we want to have a hard, challenging opponent in the AI for this more then great looking game.