I know that the theory that they retreated to participate in a Mongol "general council" after Oegodei's (sp) death is out of favor

Says who? Going back to Mongolia for the election was how Mongol politics worked. Unless there's very compelling evidence to the contrary, one should assume once word of Ogedei's death reached them, they would have pulled back, because that's how things worked.

Previous theories had held that perhaps Ogodei's death in December 1241 prompted the main Mongol commander to head home; but that's unsatisfying, Di Cosmo said, because the commander never went back to Mongolia to take part in the politics there — he ended up back in Russia.

It only doesn't make sense if you don't have all the information. Batu wasn't the only prince in Europe at the time. His brother Berke and cousins Mongke and Guyuk were all princes who had to return to Mongolia for the election, and indeed they did. Just because Batu didn't return while everyone else did means the election wasn't the reason for the army to return home?

And Batu didn't stay in the west because he didn't care about the election, he cared very much. It's just that he was trying to prevent/delay it because Ogedei's son, Guyuk was the favorite to win the election and was also a rival/enemy of Batu. He was called to attend and made excuses that he was too ill to travel. He delayed the election for five years, until they decided to hold it without him and Guyuk became Khan.

Soon after Guyuk became Khan he moved west with an army to attack Batu when he mysteriously died (suspected to have been assassinated by Batu's assassin). It wasn't coincidence or indifference that Batu stayed in the west away from Mongolia.

So. Ogedei dies, all princes are expected to return to Mongolia to hold an election. Every prince in the European invasion goes back except Batu who remains behind for good reason. But because Batu didn't go back Ogedei's death can't have been the reason for the withdrawal, it must have been the rain?