So, this achievement is found in Deepholm, and I think you're able to get the quest after hitting revered with Therazane. That's when I first got it. The requirements are as followed:
"Complete the Restless Brood daily quest in Deepholm within 90 seconds of striking the Resonating Crystal."
I got this the other day, after a few failures. First, I'll tell you what to avoid.
1. After striking the resonating crystal, don't start jumping up the rocks. Terrath the Steady will pull you down, then toss you back up. Just move over to him to make it a little quicker.
2. When you see fire on the rock you're standing on, jump to the next.
3. When you get done, Terrath is waiting at the bottom for you to turn in. Don't fly back to Therazane's Throne to turn in.
4. If you're a hunter, you don't have your pet. Get to a rock that puts you at firing range, pop cooldowns, and blow the dragon up.
Alternatively, if someone else is fighting the dragon, you can jump on up the rocks and help. You'll get credit for the kill. After you fall, hit the resonating crystal, then go turn in to Terrath for an easy achievement.
I only suggest cheesing the achievement AFTER you've tried doing it the right way. Some people have problems with it, be it a L2Play issue or whatever, so I added that in. I imagine it'll be hotfixed one day, so if you need to cheese, do so soon.