Update on my problem:
Which has gotten worse.
I read somewhere that actually Hylea was the one who ends the quest.
Then I rushed to the temple and talked to Hylea. And she ordered me to solve the "dragon" problem again?!
Well, I solved it already. Nothing changes.
I killed the Sky dragon at act III but the quest didn't get updated. So I can't end it.
The dialog option just doesn't appear when I talk to the quest giver NPC.
Is there anything I can do besides backtracking to my last backup save :/
Thanks.