For a while now, we've had answers like these ones which fail to really answer the question on their own, but just add some extra information building on other pre-existing answers. They often even say as much: "This other answer already covers everything, so let me talk about some tangential extra stuff". They're consistently from users at least moderately experienced with our site, too.
I have an expectation that answers should always independently answer the question, such that if that's the only answer that exists, it should still make sense and the question should still be considered answered.
Because of this, I've been consistently downvoting these answers and leaving comments requesting that these people actually answer the question, and then provide the tangential stuff they want to - even if it's just a brief sentence or two and a link if they want to credit another answer.
Should I be doing this? Is there a better way to handle this?