With 2 healers 2 tanks and 6 dps you should split it 2 dps either side, if interrupts dont always get done its still doable as long as you can manage the dps to kill the casters before they get 3 blasts off. The important thing we found with this setup is to send 2 casters into the air - shadow priest and fire mage are perfect for this, the mage will generate anywhere from 27-70k dps at full buff lower geared and can break that with the heroic items soon to come. The shadow priest wont be too far behind and with this tactic you will kill the boss within 2 ground phases if not 1 when geared.