Caster Limit break is also usually used in Aurum Vale against the second set of Morbol Pods during the Miser's Mistress boss. It deals damage to the boss, but also takes out all the adds, which basically have to be killed before they hatch.

They can be killed with standard AoEs, but some parties will just prefer to use the caster LB since it means the other DPS can still focus on the boss (especially if they're melee DPS.)