His shield was taking two rockets, which then left you short for the damage phase. I was struggling with the shielded centurions too, until I matched.
I did a second raid yesterday with an LFG. They'd a different take on some of the encounters. For the Gauntlet they went anticlockwise I think from cup clearing adds, then you went to your major area and cleared him before taking the orb and going in.
More interestingly for Calus, right at the start they'd have all the team stand at the door into the room. A Nightstalker would start the encounter (wearing Orpheus Rig I guess), and shadowshot generating orbs in the middle door right under Calus. The dude was getting maybe three supers off and it made clearing the room a lot easier for those with roaming supers (Stormcallers were getting at least a couple of goes)
It's was nice to see different methods of approach.