I dont know… I dont get to play too much with a wide variety of people, but I regularly put the hurt on the allies with only a 4 IPC bid, for an artillery in Lybia -the bomber is just icing on the cake for this fight… Seems pretty balanced for me there, if I dont make any big mistakes, it just comes down to the ever so slight sway of the luck of the dice over the next turn or two to see where the game will probably be heading. Anything more than that just seems OP… I would slaughter my opponent with a 10 or 15 IPC bid.
And its not like the opening is being done poorly… Russia buys inf and a few art or tanks, stomps W. Russia and takes Ukraine usually with just enough force, stacks caucuses and wrussia (i never get that one back), and trades territories using fighters until the brits take norway and ready a stack for karelia. Pull back from the japs always one country away from the dead zone, stacking in novo for mid game defense.
England usually buys some mix of navy and troops, to put pressure on germanys western front. USA starts up the shuck shuck. Standard fair really. But its simply usually enough for germany to shred africa with minimal investment, hold it until the US is forced to divert troops, at which time Japan has spread the rising sun across the entire swath of the southern pacific and the indian ocean, and is usually able to reclaim the dark continent for axis hands, while at the same time putting the serious hurt into Moscow.
At this point, the game has gone on so long that I fail to see the massive statistical difference you would get from having, say, eight IPC instead of four on G1. It really just comes down to the tactical errors your opponent makes, and how well you take advantage of them, be they ever so slight.