On PSNA I finally managed to close it by going to a different alliance's quest giver. Try talking to all 3 of them while you have a subclassed skill line equipped. I had been trying all year to close the quest, then a few weeks back I randomly passed by one of them so and it worked. I'd tried all 3 of them in the past, but for some reason it finally happened. I was able to close the quest on all of my toons that were stuck on it.