i have already same tactic on chimera here http://www.mmowned.com/forums/world-...nt-25-man.html
so what you need is: shaman (2-3 healers with Spirit link totem) 12-15 dps who will gain 100 energy on the 1st mobs (stand until 50 and don's dispell debuff) then start to zerg boss - when shadow elemetal spawns - everybody stands in 1 camp and shaman puts his totem - we made it with 2 shams so - healers hp and tanks goes into dpss hp - fight takes nearly 3-4