The Path
Once Vaelastrasz and his mobs are defeated, you'll come across a room filled with traps and different patrols. These traps slow movement speed by 80%, in addition to your attack and casting speeds. Whilst your raid deals with these patrols, your Rogues should start disarming the traps to allow players to work their way through the room towards the next floor.
You should note that these patrols reappear after several minutes, whilst the Dragonlings respawn every 30 seconds. It's imperative that your raid doesn't idle or waste time during this stage, as you'll be in near constant combat and should preserve your mana.
The Third Boss
Strategy
Lashlayer is a boss that requires, above all else, proper raid positioning to reduce damage taken. The tanks should position themselves in the corner next to the gate to avoid being affected by Knock Back, while the rest of the raid should fight in the opposite corner. This encounter will frustrate your melee classes the most, as they can only really deal damage when the boss is very low.
Lashlayer will use Mortal Strike, which not only deals massive damage to the targeted tank, but reduces their threat by 50%, forcing other tanks to pick up the slack. To prevent pulling aggro, casters should primarily use their wands and melee classes should use their ranged weapons. In addition, the boss will use Cleave to targets in front of him, and Blast Wave in melee range.
However, the melee classes can fight the boss if they are extremely careful and disengage whenever they take too much damage or build too much threat. Make sure your tanks are as bulky as possible and constantly use Demoralizing Shout and Thunderclap to stay alive.