Well, it is RNG based. However, you are not completely powerless. Higher Tailoring skill will get you high quality BoD's. I have also heard whispers that luck may effect it, but I am not sure of this. It might be worth testing out. Additionally, when you turn in a BoD, you can get another one immediately. I know what I and others do is have a second account that also gathers bod's and feed them through your proper crafter. In my case, I only have enough skill on my alt to get BoD's and no more. You can get them more often with lower skill. For instance, my Legendary crafter get one every 6 hours, but my ~40 alt gets one every hour. The alt gets generally easy ones, but still have a chance at useful BoD's. Once I stock up a significant amount, I go about filling LBoD's and processing the bad ones to get fresh ones on my high skill character. This is really the most efficient way to do BoD's. I have heard that some actually fill all their character slots and have macros/scripts to log them all in and get their BoD's. If you went through the trouble of that, you would have a massive amount very quickly.
