The report is in from Lancer on the cylinder head and valves.
As I suspected, the valves have a few.. issues.

New pictures in the gallery:
http://imgur.com/a/RhTYOAnd narrative from Lancer (I hope I have them in the right order)
1. #2 exhaust valve with 2 distinct cracks developing on the top edge.
2. Intake valves looked decent on the back side but had a few minute cracks developing on the face.
3. Deep wear grooves on the exhaust valves.
4. A closer look at the deep groove in the exhaust valve.
5. Face of intake valve showing a distinct crack on the top edge.
6. Intake valves, no groove on the contact surface.
And a direct quote: "Anyway, the basics are that the valves themselves are trashed, with cracks on the face openly visible, and with very deep wear grooves on the back side of the exhausts.
The springs are just barely inside the spec's, as are the valve guides.
All of them need to be replaced."
Happy happy joy joy..

So, my original suspicion appears to be correct.
"1. Using too much oil (compression isn't horrible though. Suspect valve seals)"