We've been running 2 dps, 2 healer setup. 1 Merc, 1 Marauder, 1 Operative healer, 1 Sorc healer. The Merc is usually the tank, when he cant hold agro on something then who ever has agro is the tank. So far we've cleared: False Emp hardmode, Battle of Illum hardmode, Boarding Party hardmode, Foundry hardmode (up to Revan, his force lightning does like 50k dmg), Black Talon hardmode. When we struggle for dps the sorc goes into semi dd and off heals as needed.