He randomly ports to one of the two alcoves to the left and right of the entryway to this balcony at 75%,50%,25%. When he ports to either left or right wing alcoves, follow him immediately, using racial in-combat speed buffs or sprint. He begins casting bonewall, and in a few seconds will complete casting it, anyone outside of the bonewall/alcove will be dead. Merc's seem to also get hit. If you have a decent run speed buff, and fight him center between the two alcoves, you should have enough time to get inside the Bone-Wall before it is complete and explodes doing DMG to anyone outside (Running down the stairs etc... does not protect you. Main thing here is to know that unless the Bone-Wall on the alcove has exploded, you can probably run through it.
This one is easier if you have a merc than duo, because the merc will finish him off even if you die. Another strategy is to have one person leave the zone, activate a merc and then complete the encounter. He is not a required mob for the daily quest, but the other mobs will not spawn until he is dead. The merc doesn't seem to lose his target, so if you target through him you can see what he is doing a bit better, and how much time you have left.
With sufficient dps just tank and spank. Pull him outside the circle, and joust the black pillars.
Achiun K'dal, Peris K'dal, Ursher K'dal Edit
Clear room first, then kill Achiun first, then Peris and Ursher last. YMMV
With sufficient dps just tank and spank
Valdimus V'Derun (Advanced Solo) and his chorusEdit
He revives the choir every 20% hp he loses. The more adds that are alive when he loses 20%, the harder his uncurable detriment hits.