Generally, I think the advantages of 2 crew over 1 come in the execution of those complex or very high workload scenarios. I listened in on a 2-ship live QRA a few years ago, think it was the BMI one, and the workload of the formation lead was phenomenal, and appeared highly stressful, almost to the point of being task saturated in my opinion.
Certainly way beyond my capabilities, regardless of the amount of training undertaken!