Flying below Vyse isn't going to kill you if an engine is inop, but it's recommended because you'll get the best rate of climb(or slowest descent at altitude) in that event. But even then, short final, when you're commiting to land, so slipping below Vyse in my opinion is how it's supposed to be in light to medium twin aircraft. I include King-Airs in this category, and the POH even has the threshold numbers to back that up.