I was under the impression that it was record against similar opponents or against the MAC-West.
As I understand it, the first tie-breaker after head-to-head is the record against the MAC West champion, and the tiebreakers after that follow the records against teams according to the tournament seeding order. But in the event of a three-way tie, you break the first tie, then re-apply the tiebreakers from the top to break the two remaining teams.