I have encountered a few issues with rehearsal marks, and default placement with other items. As you can see from the image below, in trying to prevent collisions Dorico is forcing the rehearsal mark very high up. This example has system text and a percussion legend.
With all of this considered, I would suggest that instead of forcing the rehearsal mark up, that the other objects push slightly to the right. Keeping the rehearsal mark somewhat in the default position.
Currently when this happens, a huge gap between staves occurs, which is understandable for what happens. However, pushing the other items slightly to the right should help eliminate the rehearsal mark pushing so high, in turn helping to prevent the excessive gap between staves. I think this one change could save hours of work manually resetting spacing.
At present, Dorico only considers rehearsal marks and tempo marks together and will move a tempo mark horizontally to avoid a rehearsal mark, but it can’t do this for any other type of item. I agree that it would be helpful if Dorico could handle this kind of situation more gracefully.
For text items, you can disable collision avoidance for them before moving them graphically, which will remove them from the vertical spacing calculation. You can’t do this for other items like percussion legends, but that can be very helpful in regaining more balanced vertical spacing without manual intervention.