I didn't see any of these to be able to know about outward symptoms, but they were removed because they were hazardous. Some that they looked at were already failed trees. I'm guessing some are conky and have fading crowns, and history of dead/ dying/ failed trees in the area.
I'm going to start with WA State Parks on the Arbor Crew on Tuesday. I hope to become dialed in on diseases and will try to get some before and after shots of the work. In residential arbo work, we rarely get to see the ones that are really rotten, so don't see lot of the telltale conks and really badly decayed trees.
Should all prove to be interesting.