It's possible that had the RAF gone for two pilots from the beginning with four engine heavies the carnage that killed an enormous number of crews during their training might have been tempered. The initial crewing with one pilot because for no other reason they felt they would get on together OK meant that there was no experience to draw on during their training. Should there have been two pilots then the junior one would have advanced to getting his own crew and having a good idea of what it was all about.
The USAAC seem to cope with two pilots as would have the RAF because their training system was churning out more pilots than they could use.