Burning through the shield while managing the adds is a pain. A couple of notes, when one of the adds dies and is rez'd by Lady Deathwhisper, it will come back as a skeleton. If the skeleton is a caster, physical damage dealers must kill it. If the skeleton is melee, magic damage dealers must kill it. If all other adds are down and you don't match up with the add type, you should be hitting the boss. Also, when one of the adds turns into a deformed monster... ALL ranged dps (magic and physical) should be on it. Don't wait to down the add you're on. Leave it and focus fire on the deformed add, then return to what you were doing.
A note on "Touch of Insignificance": When on the main boss, she casts a debuff that reduces the amount of threat generated by 20% and it stacks up to 5 times. This is easy to manage by having the two tanks taunt back and forth when the other tank gets 3-4 stacks. That gives the taunting tank's debuff enough time to wear off. However, the beginning of this part of the fight needs to be closely coordinated between the two tanks. When she lets loose, if both tanks start taunting to pick her up quickly, both will likely get the initial debuff which will make it difficult to get the timing of the taunts in sync with the debuff CD. One tank should be designated to tank her first. Or at the very least, the tanks need to call it out in vent when she releases. As you will see at the end of this fight, I had 5 stacks and the other tank had 3 or 4 and still had a few seconds left before the debuff cleared. The boss turned around and one shot on of our druids. :(