But that's not how torrents work - at all. Unless all 900 people are stuck at the same point and all 50 seeders are imaginary.
As soon as one leacher DL's one block he essentially becomes a seeder of that block - tho "seeder" status in the client list isn't awarded until he has 100%. So there are actually 900 partial seeders and 50 complete seeders. As long as there are more than 2 complete seeders the ratio of seeders to leachers is insignificant. 50 to 900 is a great torrent - awesome even! - and should be DLing for anyone with a good connection and proper settings, very fast!
So if it's going slow then it's either the connection, or the settings. If your UP and Down speeds are too different (like 2MB/s up and 10KB/s down) then I would also open the tracker list and delete any leach trackers that are piggy-backing onto the torrent.
Many of the torrents I DL are 40 to 2000 in ratio and I get a consistent nine or ten megaBYTES per second.