Game bugs out on iMac Late 2012

Finally managed to get the game running on my iMac late 2012, however it freezes/crashes immediately in the tutorial when encountering the 2 assassins in the hallway (the first assassin works fine).

I know late 2012 iMac is on the lower end, I had to set graphics to low in order to make animations smooth. Running OS x El Capitan at the moment, iMac is generic 2012 with 8 GB RAM upgrade, using borderless as is the default. Is it likely my underwhelming computer causing the crash or could something else be done like upgrading OS X or running Boot Camp instead on the same computer? Anything else?

Normally the first step is to check your graphic card driver. Are you able to update them on you Mac?

And also verifying the integrity of the game files.
https://support.steampowered.com/kb_article.php?ref=2037-QEUH-3335