The engagement ceremony, "Le Dinh Hon" does not cause any issues as far as the consulate in Ho Chi Minh City is concerned, speaking specifically about Vietnam. I would go so far as to say that NOT having it would draw more questions than having it. It is a well known custom there, so no, you do not appear to be "too married" as it is not a wedding. I used many photos of ours as proof of relationship, as did a friend of mine and both our (now) spouses passed the interview with no issues and are here in the US.