Vader tends to accompany many officers or others that he chposes and when he lands it is usually in demand of an audience, is it not? It would be expected that he could sense the doubt in Herald. However, he isn't that far from ideals as other soldiers. Most high ranking officera actually follow Vader because they believe in his mission. Others are there for their own reasons. Herald's doubt doesn't lie within betraying the Empire, it lies within money and power. The Rebels can't give him that and the Empire is practically giving him a mansion (in his eyes). So the doubt is that he doesn't care for the mission. Meaning it's not his goal, but it's similar to other soldiers. He was singled out because he is not in love with the Empire, but he likes it more than the Rabble Alliance... As he calls it. He follows orders without question, he doesn't secretly hate or dislike the Empire, and he has come to love ordering his troops to execute Rabbles.
Meet Vader? Not really. He was saluting and Vader stopped to question his doubt. He questioned him, he didn't kill him.
I forget, is the Deathstar in yet, or has been? I forget the time lines. How would doing service on a Deathstar sound?