The Crystallized Construct - Calls the spiritual constructs around the room to life as adds after each time he casts his big knockback AoE. Either burn him fast or drop adds as they spawn to keep the incoming damage lower on you.
The Armor of Sul - Clear all the 'an animated Sulite' around the room to spawn this next boss. He will spawn with a 10 stack buff of damage reduction. When the orbs on either side of the room begin to pulse at you, put him between you and that orb to remove 1 stack of the damage reduction. Repeat each time the pulse starts on you, from each orb, until you have burned him down. NOTE: you can't see the red beams of light if your graphics are set too low!
Sorceress Gwen'vae - She starts with a damage blocker buff via whirlwinds she spawns. Move her away from the whirlwinds she is spawning, the whirlwinds move slower then her. You can damage her while whirlwind is around her. Eventually she will summon flame pillars and adds that will go after you, as well. NOTE: The whirlwinds and flame pillars do knockback that can interrupt spell casting. Best to keep kiting as best as possible to avoid getting knocked around a lot. Pull her into the red spire rings, then hit her with your best spells.