That is what it is for me - I thought Theron did a really good job with what she had. She just managed to add some subtle touches that moved her, for me, from an emotionless character into a much deeper one than the script made her - the bit that stood out for me was when she flame-throwered the the infected guy, there was just a perfect, pained look of someone who really didn't want to do what they were doing but had to. Her acting got over to me that she wasn't just an emotionless corporate person but there was a conflicted person underneath - desperate to impress her father and be the son he never had but actually someone else underneath it.
Fassbender, for me, was also excellent though in his case the script actually helped him by giving him Peter O'Toole in Lawerence of Arabia to model himself on (an socially awkward, emotionally detached role model).

Rapice and Idris Elba were like Theron for me, they seemed to add more than just their scripted actions and words gave their character.