I have installed the mac client on an iMac running El Capitan and it last week stopped working (starting the client causes the iMac to hang and reboot itself). Interestingly, I have also installed the mac client on a MacBook Pro (Retina, 15-inch, Early 2013) which has been upgraded to Sierra (10.12.2); the client still works on the MBP.
Very very frustrating. I also play EVE Online – which in the last six months has moved their Mac version from Cider to the real Wine, maybe Anet could reach out to CCP for some help?