I must have been one of the few that actually liked it, i just kept my thumb on the A button, didnt hold to slide for too long, and basically Chris did all the vaulting and whatever on his own. it was rather straight forward
My problem is somewhere around that last part where Piers climbs on a platform and Chris just looks around stupidly for a moment (and yes, I did hit the B button) until the whole thing crashes around him.
It only happens with an online partner. I did it offline and Chris makes it easily. It's probably lag but my partners leave the game after several attempts.
that "big mutation" is called Haos, a BOW that is the final boss. The only hard part is about halfway through, you have to slide immediately due to the way the camera pans. just remember it happens after Haos blocks the way.
I'm told I look a lot like Rory Macdonald - http://i46.tinypic.com/2eyf5sy.jpg My beautiful Roselynn: http://imgur.com/IaIxgc2