I've never really felt like OU needed to root for other teams in order to get into the tournament or get a top seed. In my experience, being good is enough.
However, familiarity often breeds fondness. I like most of the Big 12 fan bases and end up rooting for them. The only teams I don't root for are Kansas (in their case familiarity bred disdain), OSU (rival, but most OSU fans are fine by me), and Texas (football hate bleeds over).