I don’t know the rest of your specs, but mine are:
Processor 2,7 GHz Intel Core i5
Geheugen 8 GB 1333 MHz DDR3
Videokaart AMD Radeon HD 6770M 512 MB
And with this Mac I can play the game, but only on the lowest grafic settings and I have until now only played on the smallest Map. I am not sure if that works. The 512 MB of my Video-card is the absolute minimum.