No it doesn't work in the sannin's case.In the Sannin's case it works ( or at least worked). In the manga it was stated only a Sannin can defeat a Sannin. And according to a Japanase game and myth they are equals: Slug ( Tsunade ) > Snake ( Orochimaru ) > Toad ( Jman ) > Slug ( Tsunade ), etc.
Oro > Tsunade or Jiraiya in 1v1.
Only a sannin can defeat a sannin?, Remind me what did Itachi do to Oro.
This wasn't even true in part one.