Forgive me if I'm being stupid, but what actually is the combo? You can use Sorin to cheat out Olivia, but you can't do it at instant speed, which means you can't do it in response to Emrakul's graveyard reshuffle trigger and can't therefore
reanimate Emrakul. If this is true and it doesn't work, you'd need a different finisher; many high-end creatures have that shuffle effect (
Blightsteel Colossus,
Progenitus, the Eldrazi Titans), but you still have some options like
Iona, Shield of Emeria,
It That Betrays, or
Void Winnower.