Not sure a big investment in diplomacy to get the Soviets on board is the best thing to do. Sure it gives then more MPPs faster, but they have so much to do to catch up, and I'm not sure if it's good to speed up their entry into the war if they are still under prepared.
Having said that, could be a good idea to invest in getting the USSR readiness higher once their mobilisation starts to go up due to the increased German presence on their border, as you know then Germany will be launching Barbarossa soon. Although it's a short window, 6 months max, but a lucky hit here and there could help.
As for the AAR, this is shaping up to be a excellent one, and can only help SC3 in general. I always consider the number of AARs in a games forum to be a good indicator of how much interest there is in a game.
A lot of top Axis player delay Barbarossa as much as they can, which usually means Autumn 41. The USSR collect so few mpp compared to Germany that they don't see the incentive to go earlier than when its mobilisation forces them to. The extra income helps the USSR jumps start its research effort but also forces the Axis to go Barbarossing earlier than they would wish. I wasn't planning to do uberdiplo when the game started but when it became apparent they Germany had tied its chits in Spain, I saw an opening.