If 25% of your group has no clue on what to do then you are likely to fail. For this reason groups of random players, often referred to as PUGs (pickup groups), are often a failure. The solution to this problem is joining a so called guild.
Proteus is the second boss in the tier 2 raid Planebreaker Bastion. The boss cannot be tanked and takes 90% reduced damage unless stunned. Quicksilver Constructs need to be damaged down quickly and tentacles need to be frozen with ice crystals. Gameplayinside explains all the tactics in this guide.
The purifier soul is one of the most awesome heal specs. Instead of just responding to damage you can learn to prevent it by timing your absorbs. When your gear is good enough you can run Expert Dungeons without the party ever taking damage. There are many talent builds out there but this Blaze and Flame build is my absolute favorite!
Warden Thrax is the third boss in the tier 2 raid Planebreaker Bastion. Killing this boss requires all raid members to pay close attention. It is important that you survive the mecanics to be able to burn Warden Thrax down when he reaches 11% hp. Gameplayinside explains all the tactics in this guide.