just did it last night on my Warlock...no issues. Must be a situational thing.
It is indeed. The original problem seemed to come either from doing the previous quest when in a party, or 2 people completing the quest in short succession on the same channel. Both applied to me. My friend completed the quest and Jill appeared and all was normal, I completed it and no Jill. Because at this point I've already completed the previous quest and can't redo it, I'm stuck.
This is something that support has been notified about in detail. Why it's so difficult to fix I have no idea. I've opened a number of support tickets over the last several months since Chrysalia was released, and mostly the response has been that they've notified the developers and have no idea on the status or if/when it will be fixed. I was cautiously optimistic about the patch that was supposed to fix the Missing Loub quest, but apparently by "fix" they meant "people not already impacted by the bug".
It would be really awesome if they could take some time and fix this. Here's hoping.