Buggy Mac Client
You might try changing your graphics presets to best performance. This is by no means a suggestion that your graphics card is subpar, but there is a long running bug (~2013) in the mac client graphics for which the best performance preset seems to be a functional work around. If that does stop at lease the first error, you could try adding back in graphics features one at a time until you start crashing again. From my own testing I can run a single setting on high with everything else where the “best performance” set them. When I start digging into 2 optimal settings I start having problems again. It is tragically bleh in appearance but at least it mostly functions. Good luck.
mid-2011 iMac; OSX 10.9.5; 3.4 GHz Core i7;
16GB RAM; AMD Radeon 6970M 2GB VRAM
16GB RAM; AMD Radeon 6970M 2GB VRAM