Standard single target on Tectus. FoK the small adds for more combo points to slam into Tectus. Don't FoK during dance.
Phase 2:
Keep rupture up on both Shards + the big add. Crimson Tempest (CT) when you have rupture up on all. FoK to gain combo points. Auto attack the priority target. Use CT before rupture to make sure you have bleed up on all targets. Dance on one of the targets that will last a little while (If one shard got more health than the other this is going to be a good target). Save Shadow Reflection (SR) and second potion for next phase.
Phase 3:
Get CT up on all targets. FoK once to gain 10 cp. Potion (+ on use trinket) + SR. Vanish. Go HAM with CT and FoK. Don't stand in shit. Laugh at the other melee dying because they need to stand between the mobs. Evasion if the tanks die.