The dragon's scales weren't shiny. Yes, we the readers can understand in retrospect that the OotS shouldn't have killed it, but considering the OotS lives in a world where all chromatic dragons are regarded as evil by default, I don't think we can blame them for killing it; according to the knowledge they had, that was the right thing to do. When that strip first came out - when dragons were just another fantasy monster and we had no idea that the mother was coming back - did anyone think "oh hey, maybe they shouldn't be invading another sentient creature's home"?

So V saving the group from the dragon is not an insignificant help on V's part. Even if we disregard that fact and say that the Order was doing wrong by being in the dragon's lair in the first place - that doesn't change the fact that without V, they might very well have ended up dead. That counts as a contribution to the party.