It's fairly obvious when Low Persistence isn't working. The display is much brighter and there's lot of blur.
That did it! Low Persistence enabled for me after loading Titans of Space first. Very odd, but I'm extremely happy to have a workaround until this problem is officially fixed. Hopefully this will no longer be an issue once they fully support Direct Mode.
I am definitely running at 75Hz. Doing more searches online has found many people who're having the same issue. As mentioned above, by first running another Oculus demo that allows toggling of Low Persistence seems to act as a workaround for this problem.