[xequence]

that leaves only 2 total GBs of upload left to be shared among the 12 leechers.

Yes, if only twelve people are going to download it. I havnt made a torrent that had only 12 downloads though. On the site I upload torrents to, my least downloaded torrent was 121 downloads and my most is 12,545. The others are in between, mostly in the couple thousands though.

If each person downloading that torrent only uploads 0.3 of it, it will be dead fast, even with the 10GB from the original uploader. Especially on trading sites like this where it is often only 10 or less seeders and leechers, you not uploading some parts of a torrent means someone else misses out on it. And that is a chain reaction - the potential downloader cant seed to someone else who wants it also, and same for that person.