I am having similar issues and can report a bug to apple if needed.
At that time I was running Yosemite. After trying everything I could for the next few days I upgraded to El Capitan. That made no improvement to the lag and in fact introduced a bug that crashed the game every 10 minutes. Went to the forums again and nothing I did seemed to help.
You have enhanced edition? Then drop your crash logs to support@larian.com please.
