Two points:
1. "singling up" in the two engine helicopters I flew was an emergency procedure. The problems with restart may have been overcome in the last 30 years, so my data point on the fatal mishap where a crew singled up, and when the operating engine gave up and the crew didn't successfully restart ... might be more due to old tech. (The root issue is that the engine still wind mills while flying even if shut off ...)
2. Regarding the A400M recent mishap, one hopes that, as I said, the appropriate lessons will be learned and such things removed from cause/risk factors in other products the company presents for sale.
One hopes.