The raid tank group is the most important group to put together well. If it is not, no matter the number of nukes you have, you are all going to die. Our personal favorite setup is a tank, two bishops, two SEs, two EEs, a sword singer, and a worrier. With Silkroad gold, you have plenty of MP Regents for the bishops, your main healer and rechargers for the tank. Plus, you have two people with a 30% heal.
When the raid boss does 300-1000 damage a hit to a tank after the shield block damage depending on your level and level of the boss, of course cheap silkroad gold are very important. Alternatively, you could swap out one of the rechargers for a BD, who does only song of concentration. Alternatively, swap out one of the healers for another tank. At the very bare minimum, we would recommend two bishops and two rechargers on the healer side. A sword singer is not optional: song of earth, warding, and vitality. Because the 30% heal is so important for healing in a raid, having a tank with the most HP is usually more useful than one with a slightly better armor set.