It's a pretty basic fight.
Have a main tank with some healers stay on Tarn Icewind the entire time. At the start of the fight you get all the main DPS (rogues, wizzies, rangers, etc) on 1 crystal at a time till they all 4 drop. During this crystal killing, waves of 2 ferans will spawn. They hit for ~1kish. The non-main DPS people need to drop off the crystals when the waves spawn, to kill the 2 ferans. You should be able to kill the 2 ferans then have everyone run back and assist killing off the 4 crystals for a few seconds before another wave of 2 ferans spawn. When they spawn, non dps people break off to kill the 2 ferans. Once all 4 crystals are gone, the DPS people get on Tarn Icewind with the main tank and start dropping him. Rest of the raid continues dropping the 2 feran waves as they spawn, helping kill Tarn between waves. Once all the crystals are down it shouldnt be more than 2-3 waves of ferans till Tarn drops. Hope this works for you. We've yet to have any trouble with this event so far doin this strat.
Muttonchops Cunninglinguist
Herald of Morden Rasp
Inverse Logic Guild