Yup, talking to the right person ... because it just worked. Why it didn't work the last 12 times I tried, I'll never know. I didn't get any new notices when I walked up to Melanchion's gate going through it 5 times in a row - but this time, the person in Fort Mon gave me the end of the quest.
I don't even care why now, I'm just glad it's off my list.
Off to die at the hands of the vah-whatevs again.... "sack tenevra" my left foot, mr big shot dragon.