pcimage wrote:
Spin down mean bad heads 99% of the time

Thank you! That's good to know. Putting that in my notebook.

Day 2 so far has left me with many more questions.
It's so odd though. I have four of these drives from March 2012. They were all in a WD Sentinel box, supposedly. When I purchased them I thought maybe it was going to be some super easy fix (eg.disable PUIS). Maybe power anomaly zapped the heads (or preamp?) on all four of them? They all exhibit the exact same behavior audibly and in diagnostics.