>independent invention was a defense (as it is supposed to be, but in practice basically never is)

It's actually not a defense at all and isn't supposed to be. Its sort of like a prize for inventing it first.

It's only a defense if you publicly disclosed it before patentee did. Secret use was a defense if you invented it first (and didn't abandon or hide your invention when it was ready), but that was changed with the America Invents Act.