There seems to be something wrong with this game. I play it on an late 2013 27" iMac with the fastest i7 CPU you could choose at the time, 16GB RAM and the GTX 780m with 4 GB of VRAM.

I should be able to run the game on high settings, but the framerate drops dramatically to slideshow proportions once I get into a fight with more than one enemy. Exploring is fine, cutscenes are fine, but when enemies appear the game gets choppy as hell. Turning off some graphical settings somewhat makes this better, but then the graphics look absolutely horrible.
I don't understand this problem at all. Granted I don't really play a lot of games, but I could run Bioshock Infinite and the new Tomb Raider smoothly on the highest settings those games would let me use. Fortunately this game was on sale this weekend so I didn't throw away much money.