Clearing the Way
After Sartura is defeated, you'll have to make your way through a long tunnel lined with elite and non-elite mobs. Nearly all of these mobs will respawn quickly, so you should have one tank lead the way and another to protect your tail while your raid progress through the tunnel in a single group. However, you should take the time to kill as many creatures as possible as you progress through the tunnel.
Once you've made it to the end of the tunnel, you'll be able to reach an alcove on the left where you can regenerate HP and mana and can safely prepare yourself for the next boss.
The Third Boss
Strategy
Fankriss is not necessarily a complicated boss, but you'll need to react quickly to defeat him. Like his smaller brother, Kurinnaxx, he will inflict Mortal Wounds which will reduce healing received by 10% each stack. After receiving 4-6 wounds, you should change your main tank. Be sure to repeat this process until the end of the encounter.
Once every minute, a random player will be teleported and Entangled in one of the 3 smaller, where they will be attacked by mobs. You'll need to rescue this player quickly while your DPS kill these adds, as they deal 300 damage to tanks and 800-900 damage to cloth users.
Finally, Fankriss will summon Spawn of Fankriss during the fight. They must be killed within 20 seconds or they will enrage and wipe your raid.