Sorry about the long hiatus, took me a while to get around to looking at this again. I ended up swapping the wheelset from my daily driver, no change... Swapped out for another used rear derailleur I had laying around, no change...
Turns out it was the freaking brand new chain! I swapped it out with a used one that wasn't all rusted and nasty, checked it with a gauge. (Came off another bike altogether, not from either wheelset I used.) Worked perfectly on the first try out of the driveway.
Crazy, I use a KMC Z-51 on the daily driver and have used them multiple times for friends and family. Might start upgrading to the KMC Z-72 out of paranoia now...
Thanks everyone for the help.