The spell parsers haven't updated yet (a fary cry from the old days when Lucy would update with every Test patch!) but it looks like a 10%, 20%, 30% minimum damage modifier.
As Fero7 and up have a 200% minimum damage mod, I'm wondering if a) whether they'll stack at all and b) even if they do, whether the DPS increase will be even remotely noticeable.
I can't answer either, sadly, as I don't have a melee class to test with and I certainly don't have a Fero7 item!