The problem I see for Cain is that he got rocked in every round, and the fight was standing for less than 1 minute each round. So his striking defense is really poor. And like other mates here said, if he tries to take Lesnar or Couture down, he'll have a hard time doing so, and he loses the standing battle against either of those guys, and against Mir or Big Not, he'll get subbed if he spends 12 minutes on the ground withough finishing the fight.
I saw a fight that, despite the dominance of Cain, it could go the other way at any time that the fight was standing. And that's not what a "dominant" fight should look like.