I hear you, Steve. Sad to say I relate to your frustration. Can I vent, too? I've experienced the arrogant drs, the content to do nothing drs, the "try this over the counter med" drs, the diagnosis not made until it's an emergency (usually due to previously mentioned attitudes). And, sigh, the "since you have a history of depression, there can't be anything physically wrong" drs. Then I've watched family members go through the same stuff. As angry and aggravated as I've been for me, I think it may be even harder to see it happening to someone you love. I guess it may be because we have even less control. I'd like to beat the crap out of those moron drs but it will change nothing.
What has helped me in these times is to do just what you've done---vent. And also to do something physical to burn up some of that energy and make it more manageable. Then continue being there for Diane.
I wish you the best,
Bee