According to the Adobe engineering team, the problem with 100% CPU and slow typing in the Mac version of Dreamweaver CS6 has been solved in the 12.1 update for Creative Cloud subscribers. If you are a Creative Cloud subscriber and haven't installed the update, go to Help > Updates, and follow the instructions onscreen.
NOTE: The 12.1 update is currently available only to Creative Cloud subscribers. Adobe is working on a solution that will be made available to owners of a CS6 perpetual licence. An announcement will be made when it becomes available.