My group was ilvl 221-223.
DRK, WAR, NIN, MCH, MNK,SMN, WHM,SCH.
If tank gets 1 shotted by arm he still has the debuff from the boss, so the OT will deal with the first ones. Tank buster needs mitigation/cooldowns. You wanna do the double buster with 2 tanks when orbs are out, but obviously share them while hes outside his barrier. The ot do some cooldown on the first sets of orbs while me would adlo him, since you have ast you need to give him the shield buff (the heal shield). There are times buster/double buster will happen when a ot or mt tank orb so need to heal them asap. Usuauly the orb thats gonna hit mid, means there will be a tank buster or a double buster, make sure both tanks are top on HP.