Just make sure you set a worker difficulty on bitminter.com for their worker that is the same or higher than the difficulty set in the dragons' configs, to prevent them from throwing away valid work.
Is this the Minimum difficulty ? My worker's Min.Dif. is set to 1. What should the value be? Anything to do with CGMINER?
This is only for Dragon ASIC devices. I'm not sure if there are any other ASIC machines with the same problem.
The Dragon machines have a broken implementation of the stratum mining protocol.
With Dragon miners you have to choose in the Dragon miner's config which difficulty to mine at. The server will tell the Dragon miner to switch difficulty. Dragon miner doesn't care. Dragon miner will mine at the wrong difficulty and throw away most of your work.
Example: If the pool tells your Dragon to mine at difficulty 32 but the device's config is set to difficulty 512, then the Dragon machine will happily throw away most of your work and the pool will show you mining at a very low speed.
Solution: set the minimum difficulty for your Bitmitner worker to the same difficulty you have chosen in the Dragon miner config, or higher. You can do this under "my account" -> "workers" in the bitminter.com website menu. Click the gears icon to access the settings for a worker. Also contact the manufacturer and ask them to properly implement the stratum protocol.
If you have one or more of these horribly broken machines, make sure you follow the solution above.
If you don't have this specific mining hardware, don't worry about it.