While not in Central Oregon, the John Day River is close enough for a long day trip or easy overnighter and has been a focus of mine for many years. I learned to Spey cast on the John Day and have had some excellent steelhead days on this undammed river draining a huge watershed. Of course, the John Day is suffering like so many other rivers in Oregon, primarily due to irrigation withdrawals and other impacts from by agriculture, timber, and development.
The Oregon Department of Environmental Quality is starting a far overdue assessment of temperature standards for the John Day. Better extremely late than never, I guess. It will take decades to see progress but at least they are starting something. I have tried to participate in these sort of things as a member of the public in the past but no longer have the patience for the politics and bureaucracy. (Note that the rulemaking advisory committee does not have a single member from an NGO representing fish or the environment.) If you want to follow along, however, here is the ODEQ webpage on the effort which includes information on how to watch meetings and here is a lot more information on TMDLs.