Four Play

Extremely easy achievement.
Completed this on my 583ilvl Fury Bloodelf warrior.
1) DPS boss till he reaches phase 2 @ 80% health that is.
2) Wait for him to spawn a small lightning add called a Stormling.
3) If lower geared preferably push boss to 40-50% keeping add alive.
4) At 40-50% Boss HP kill the add giving the boss a buff called Feedback, which lasts for 30seconds.
5) Nuke boss, note that at 30% he will shatter the platform and you will have to fly and kill him.

Extremely easy :)

As for how to get the actual achievement; Feedback is a stacking debuff that goes on Al'Akir when you kill the Stormling adds in phase 2. The Stormlings only spawn until he reaches 30% and the debuff only lasts 20 seconds. So to kill him while he's got the debuff on him I guess you have to keep one of them alive for all of phase 3. The adds do AoE damage which prevents them from being melee'ed so keep it tanked in the ranged camp and kill it just before the boss dies, and this achievement should be no problem.

I can tell this is gonna be a favorite of trade chat...