Here's the part I don't really understand about the Mandarin...
Spoiler:if Killian's the mastermind behind, why would Slattery need bodyguards to take him to Killian's house, dressed up with a cloak and looking as if he indeed is the "master"? Is he required to keep up the playacting even in front of the person who hired him (Killian) even when no one is around? Slattery certainly was acting as the real Mandarin and big boss in that instance, while Killian was just a partner in crime/pawn.
Because of that, I thought that the Mandarin twist was done very poorly, and have a feeling that it may have been something added later on while they were in e filming process maybe..
Spoiler:
The way I saw it he was high on drugs. Remember he didn't even know that anyone was harmed during his 'performances'? After he shot the guy in the head.
Plus Killian says 'Everyone stay clear, no one look him in the eye. You know how he gets'. Or something like that.