The one tricksy thing to watch for is the arcolith’s taunt/challenge attack, in which he plants his sword in the ground and slams his gauntlets together. If the arcolith’s next attack following the taunt doesn’t hit anybody, he will immediately start spinning! NOT GOOD! So, tanks, make sure to absorb the hits -- don’t dodge or sidestep them. None of them are especially threatening for an endgame tank, and the risk of forfeiting an entire pillar is totally not worth it and really the only way for an otherwise capable group to fail this encounter.