The Shattered Halls Trash Mobs
Understanding the trash mobs in the Shattered Halls is the key to success. Nearly all of the trash is Orcs (humanoids) but they come in all shapes, colors, and types.
Legionnaires are the mobs to look out for - they hit hard, are immune to crowd control, and can make your life miserable. They are always found standing or patrolling with buddies, but in any group they are in, they must be killed first. If you kill one of the Legionnaire's friends while he is still alive, he will simply call out another one to fight against you.
There are several places in the Shattered Halls where you will fight groups of 5, 6, or 7 elites at a time. Knowing which ones pose the most danger ahead of time will help you to succeed. In each of these large groups there will always be a Legionnaire. The rest of the group make up is a random mix of the following:
Dark Caster - One of the more dangerous of the mix. They will not pull with the group, but rather stand and start casting. They need to be Silencing Shot, Silenced or Counterspelled. They will use Fear, AoE attacks, and Shadowbolts, and do very high DPS. Once safely away from any additional mobs, they need to be killed or crowd controlled.
Acolyte - Acolytes heal and shield allies, as well as cast Mind Blast. They have low health and armor and don't do much damage, so they can be crowd controlled or killed off first. You definitely don't want them healing, though, so make sure they are dealt with.
Sharpshooter - One of the most annoying of all, the Sharpshooters favor Scatter Shot, which will target a random person and confuse them, effectively crowd controlling someone in your party for several seconds. This is detrimental, especially when used on the Healer or Tank. Sharpshooters can be crowd controlled, but really should be killed off ASAP.
Reaver - Reavers deal high melee DPS and Cleave, making them quite dangerous. They are the ideal target for Mind Control as they can be just as effective when used against their former allies. They need to be tanked and are a high kill priority.
Savage/Heathen - Savages are also a melee class but they do not do as much damage. However, they use Pummel, and interrupt that can lock down a school of magic for several seconds if it strikes at the wrong time. Savages need to be diligently tanked, as they can ruin crowd control and healing if left on the loose.
Brawler - A melee DPS that casts a curse that increases damage taken. Decurse is priority, but the Brawler can be one of the last killed.
Convert - Non-elite, low health, uses a bleed effect. Can be easily killed very quickly by one DPS. Doing so saves trouble.