Sence the Patch blizzard has nerfed the way to do the achievement respec your elders, a couple of minutes ago me and a group ( ill list basic makeup after ) did it a new( to us maybe not you) way, ALMOST the same way as kiting the boss the entrance and dps racing him down.
The make up was
resto druid
resto shaman
fury warrior
frost DK(tank not dps)
and mage
2 healers 1 tank 1 offtank/dps who can OT and 1 real DPS for the boss
So what your going to do is have your 2nd healer ( doesnt really matter) stand in the room u cleared before the boss VERY far away
Start the fight as normal but when the first guardian spawns have your fury warrior go sword and board and grab the add and pull it to the other room where the resto shaman is
it is KEY that your healer on the boss get healing aggro from the adds he spawns(not the guardians) or they will go on your 2nd healer and kill him because they are immune and cannot be tanked ( because the guardian is near them)
so basicaly you 3 man the boss and have the 2nd healer and fury warrior tanking the adds. can be very long if your 1 dps on the boss is poorly geared -_-
i appologize in advance if you already knew this, but our group didnt and the strat we read told us to kite him all the way to the entrance ( which u cant anymore sence he enrages if he goes to far )
EDIT: i forgot to say why u pull them away well obviosly the boss is immune when they are to close so u pull them away for those who didnt know