Having qBT decide what's a very overseeded torrent...that's not so simple.
Trackers, DHT, and PEX lie about seed and peer numbers present on a torrent.
Counting just the connected to qBT seeds would be a decent start...but...
Many seeds that connect will not upload to you (for a long time at least) if there's 30+ peers already connected to them.
Many seeds upload very slowly due to low upload speed max possible, low upload speed limit set, and also uploading to too many peers at once on the same and/or other torrents.
These seeds (and many peers as well) are like dead horses...how many do you need to pull a cart quickly up a hill? And beating on them won't make them pull faster.
If qBT had the "smarts" to grab common pieces (especially 1st and last pieces) from other peers, that alone would help take the load off seeds.