For the initial HARD adds, I'm afraid your options are limited. You'll need to do everything in the book to pick up adds and that will include taunts, Death and Decay and Death Grip. Anti Magic Shell will work wonders during the ones with mass Mages and debuff prevention. And go with an order with killing adds. I find that Priests > Mercs > Foot > Mages > Marksman is a good kill-order because of their urgency to kill rises with what they can do. Priests heal all the adds if left unchecked. Mercs can random aggro, stun and rip clothies. Foot are just a big elite with beats. Mages AOE a bit but are avoidable to take much damage. Marksman can freeze random people but only for a few secs.
For the gauntlet chase, blow the ghouls then just hold the Abomination but don't let the DPS focus on that. Tell them to focus on the Witch Docs as they are the main brunt of the damage. The Abominations are the ball and chain of the encounter. You take them last because by then the main threat will be gone.
Hope that helps.
Healing is the source of life. Without it, you're left with death.