Why no sundered
Looking through the list of (severely limited and lacking) companion and player skills, I noticed that the only ones that are able to apply the sundered condition are companions. At least for a mage ...
Forum Discussion
Those skills are limited by class. Rogues can apply Sundered, and detonate Overwhelm. Warriors can apply Overwhelm, and detonate Weakened. Mages can apply Weakened, and detonate Sundered.
The player character is a little more flexible; a Warrior can learn to apply Sundered, a Rogue can learn to apply Weakened, and a Mage can learn to apply Overwhelm. But there are still limits. You won't be able to do all things on all classes, so you will have to rely on party composition if you want certain skills to be available.
