For Titan and Warlock keep flying in big circles on the edge of the arena and grapple punch Psions, it will keep you alive and generate special ammo. Occasionally fire Witherhoard grenade at Calus, keep this up as your main strategy. Bring a Machinegun as your Heavy for ad clear or for when the Tormentors spawn in. Machinegun mag-dump the Tormentors. For phase 2 of Calus use the initial strategy and try to avoid getting smacked, Strand-punch spiderman your way in circles and keep chipping away at Calus with a shot from Witherhoard. This method works but can take some time to do, it will need Witherhoard, without Witherhoard it will take way longer but may still work as a strategy. Always keep running and grappling into Psions, its the only way to stay alive. If you need to, use the long arena platforms for the Tormentor fights as well as the half-moon elevated platforms. Note that for the side platforms it will require heavy ad-clear. For all classes use super on Calus, once it recharges again you should have it back in Second phase to help kill him a bit faster, I usually save the second super for when he is almost dead to finish him off. For any Hunter, good luck.