They must be banned from the post season. Anything not keeping them from the playoff is not a punishment. Vacating wins means nothing to anyone except record books. Players, coaches, and fans will only respond to losing a chance at a title, or even a bowl game.
Millions of dollars are kept from their program, players who came to play at the highest level no longer have that motivation and lose chances to be seen on a national stage. Fans lose interest because there is no chance to win anything and the regular season doesn't matter.
Two to four years of postseason bans, including B1G Championship, should be the minimum. That's the only real lever the NCAA has.