I have an early 2009 mac pro, but flashed so it thinks its a 2010.
My system specs are:

OSX 10.14.1
Early 2009 Mac Pro (flashed firmware to 2010) ... not sure what, or if this matters
2 x 3.46 GHz 6-Core Xeon (Dual X5690)
64 GB 1333 Mhz Ram
AMD R9 280x

So, from a hardware standpoint, there should be no issues here. In fact, I know I can run the game on the highest settings on this setup because I've tried it in windows. I no longer have access to the windows partition and would very much like this to work on my system. Currently, the beta is not working for me. I've sent my crash data to the team.

Thank you.