Can someone explain this talent to me.

"If the Player Character fails a Fear or

Pinning Test, his Comrade only fails if the roll was a double."

As i read it, it looks like it saves my comrade from auto-failing fear tests when i fail them. Am I interrupting it incorrectly? It is okay, I guess..but it doesn't seem like a tier 2 talent. And it feels like the Iron Discipline in Deathwatch would fit in perfectly here for the sergeant.

It sounds good to me. If a comrade suffers fear, he doesn't hang around; he leaves the combat, meaning you don't benefit from him at all.

It looks like a stronger version of the Dark Heresy Iron Discipline talent since your "minion" only fails on a roll that shows doubles.