Heroic Portal Keeper Hasabel

Tank

Position Portal Keeper Hasabel against one side of the platform. Move her to the other when Collapsing World is cast.
Taunt off one another when the Reality Tear debuff expires, usually around 3-4 stacks.
Maintain threat on all adds that spawn from the Transport Portal.
Move out of the lines created by the Felstorm Barrage.

Healer

Stand 30-35 yards away from Portal Keeper Hasabel in a group to avoid excess movement when Collapsing World is cast.
Be prepared to top the raid after the Collapsing World cast and when Reality Tear expires on the tanks.
Move out of the lines created by the Felstorm Barrage.
Be prepared to out heal a substantial amount of incoming damage when a portal is empowered.

Damage

As ranged DPS: Stand 30-35 yards away from Portal Keeper Hasabel in a group to avoid excess movement when Collapsing World is cast.
As melee DPS: Follow the boss out of the large Collapsing World circle as she is dragged across the room.
Focus down, crowd control and interrupt all adds that spawn from the Transport Portal.
Move out of the lines created by the Felstorm Barrage.

Platform Players

Tanks should always try and leave the main platform just after tank switching for the Reality Tear debuff.
DPS should try and have some cooldowns available to quickly kill the mini-boss on each platform.
Always allow the tank to engage the mini-boss first.
On the Fire platform: Vulcanar - 90%
Interrupt Flames of Xoroth & Unstable Portal.
Move away from the Supernova explosion zones.
On the Fel platform: Lady Dacidion - 60%
Interrupt Unstable Portal.
Stack underneath the boss to allow the healer to efficiently heal the Poison Essence.
Attack and destroy the webbing around the player targeted by Felsilk Wrap.
Healers should keep all players above 35% health to allow them to survive the initial Felsilk Wrap damage.
On the Shadow platform: Lord Eilgar - 30%
Bloodlust to kill the mini-boss as soon as possible.
Interrupt Unstable Portal.
Stack underneath the boss to be able to target him, as well as allowing the healer to efficiently heal the Corrupt damage.
Dispel the Delusions debuff when you need to heal, otherwise keep it for as long as possible to benefit from the mana restore.