I didn't watch every game from this past season, but the only team I remember running anything close to the eligible/ineligible formations that the Patriots used in 2014 playoffs was Baltimore. The Bengals ran some plays with unusual formations (center and QB in the middle of the field, the other linemen and receivers split out to the right and left), but not the same thing. The Patriots didn't even use it.
What is Baltimore's obsession with this play? It's not used often and, when it is used, good teams can identify and defend it. Why doesn't Harbaugh spend a little time on that instead of seeking more and more legislation around the play?