We're currently in the process of making further difficulty adjustments via hotfix to the following encounters:
Ignis the Furnace Master
The Assembly of Iron
The difficulty of these encounters is being lowered in multiple ways. Some of the adjustments are live already, others will be live soon. Note that some of the spell tooltips for the encounter will not reflect the hotfixes being deployed until the next patch. As the hotfixes are deployed, the Service Status board will be updated. You can check the current hotfix thread here:
Further adjustments are highly likely to some of the other encounters in Ulduar, but these were the highest priority encounters for us. We want to allow additional players to experience more of the cool Ulduar content.