Well, I travel a fair amount in parts of Asia, and there are some amazing Hyatts there. Many of them treat diamonds quite well, and a few don't.
My favorite Hyatts in Asia so far are the Park Hyatt Tokyo (of course) and the Grand Hyatt Shanghai, but the Park Hyatt Seoul and the Grand Hyatt Tokyo are also well worth a visit. At the HR level, I have been treated quite well at the HR Xi'an.
I don't have any experience yet with the GH Hong Kong, but will be there for the first time next month.