Dave,
"If I turn a circuit off and it runs into a conduit (in the distribution panel)with five ungrounded conductors and three grounded conductors, I cut the power to all the ungrounded conductors."
Good practice, and it still doesn't guarantee you won't have a problem. I've seen many cases where more than one conduit leaving panel went into same jbox.
One of the reasons I am strong advocate for identifying every gounded conductor in every jbox, panel, or anyplace it can be seen.
