Thank you all for your comments.
It takes a while to figure out how best to play each Regime and experience does help.
For Germany, the first important thing is to get off to a good start on the Russian front. In my latest game these were the Russian/German losses in June 1941:
Soft Mobile: 31/1
Following those losses, the Russians have to retreat, seeking to delay the German advance by taking good defensive positions, especially behind river lines. Russia has also been forced to use fairly low experience recent builds to hinder the Axis advance. Meanwhile the Axis, who control the air, continue to gain experience and it is this, more than numbers that gives Germany the edge in the opening year or two.
Admittedly, German advance in the scenario is slower that it was historically, but all my attempts to speed it up resulted in Russia getting swamped. For comparison, in my game in August 1941 the Germans are 4 hexes from Minsk and it will fall in either September or October. Germany/Italy is also threatening to over-run the Med (and they actually did so in my last game).
From the production graph, I noted that German production was around 800,000 and noticeably below Russian production. At the same stage in a previous game, German production was 1,276,900 and was a little above Russia. This probably relates to developing ore mines quickly and building factories as allowed by construction points.
Construction points are a recent addition and addresses the fort-fest that Russia could indulge in early in the game.
Nonetheless, it is entirely possible that some further balancing is required. I look forward to all comments and criticisms and will take them on board.