It was the pushrod. Rolled across a flat surface, it was obvious it wasn't straight; there was a 1-2mm "wobble". New one's only $40, but I decided to try and straighten it in a vise with soft covers on the jaws.

A little mark w/ a sharpie on the "high" spot, clamp it in the vise, a couple of tugs on the rod, another roll across a flat surface, and guess what? Straight. Reinstalled it 2 nights ago and just put a quick 120 miles on the bike today.

...NO LEAK.

That's one of the reasons I love Ducatis...you learn something new every day!