Armillary's solution worked for me too. I had already killed the troll king, and changing the hex values to 00 made it so I got the quest from Brandon, and the Tenebrium container. I then just put 5 Tenebrium ore in the container and handed it in, and voila, Tenebrium skill for everyone!
And as for Larian, please change this quest so it is possible to get the Tenebrium skill on all your party members without this quest. The one skillbook just isn't enough, as I read it with my main, a mage, as soon as I picked it up, which I didn't realize until much later, when it was too late to return to a previous save!
In any case, thanks Armillary, and let's hope this doesn't result in a bugged save later on!
