I've had the Titan extreme quest (Quake me up before you O'ghomoro) for months, and haven't been able to complete it. Last night I ran it and finally had a group that could live and dodge through it. Unfortunately, the quest wasn't in my quest log. Now since you need the quest to be able to get into Titan extreme and I have the achievement, I'm a little baffled. I haven't abandoned any quests, and its been on my screen for a long time.