Heroic Archimonde Kill

My guild raid team, for which I tank, finally got a heroic Archimonde kill with the help of a few friends from another guild.  Many of my team think we don't have the right combination of classes to defeat him on our own, we don't have enough ranged, but we did once get him to 4% so I think tactics are more of our issue. 

Despite this, the kill was nice as you get an achievement Ahead of the Curve: The Black Gate.  Also if you loot the boss you get a quest item Remnant of Chaos which after a short quest chain rewards the Reins of the Grove Warden mount.

Remnant of Chaos Quest Line

The remnant of chaos starts the quest Shadow of the Defiler, where you must travel to Moonglade to speak to Malfurion Stormrage.  Malfurion is standing with Keeper Remulos at the Shrine of Remulos.  He asks you “where did you find this?”.  He gives you the quest Dark Waters.  You must accompany Malfurion to the edge of Elune'ara to reveal the nature of the remnant of chaos.  Walk with him he will wash the remnant and then ask you to return to Keeper Remulos.  On your return Keeper Remulos will reward you with the Reins of the Grove Warden.