The main damage source is the intermissions that happen at 70%, 40% and 10% health. While the clones are alive, the entire group will get pulsing damage from Penalizing Burst. The damage ramps up as time goes, so it can be beneficial to put some quick ST damage early while damage is low to reduce the duration of the phase, and then go into your cooldowns.

The main damage event of the fight is the Consumption and the resulting Anima Rejection damage on the group. It happens at 70% and 40% health.

The biggest danger however, is likely to be the Marked Prey that will cause all the worms to crawl their way to the target. Plan for this to happen as often as every 35 seconds. Control tools are best here, as well as using Externals and big ST cooldowns if the worms reach their target.