I side with @part12studios on this one. Game performance on Macs heavily degraded since, I dunno, A17, I guess.
I have a macbook pro with 16Gb ram, 2,6 GHz 6-Core Intel Core i7 CPU and Radeon Pro 555X 4 GB graphics. Game used to run A16 with 1680x1050 resolution on settings above medium and had ~55-60 FPS, rarely below 50. Now with res 800x600 and lowest possible settings I can barely get 30 FPS. And sound. Sound is always dithering, been broken since ~A17 too, I guess.
Devs have really messed up Mac performance, and it doesn't look like they're willing to do anything about it, which socks.
Basically, game on Macs in now in unplayable state.