This is incredibly useful! It lets you know what spells nearby NPCs are casting so you can choose what to interrupt with a stun or a bash.
With a high poison resist, I don't care if the NPC shammy is trying to poison me. But if he's trying to gate out to bring back 10 of his buddies, THAT I want to interrupt. Same thing for NPC clerics. I don't worry about their nukes, but if they'e casting a complete heal, that needs to be interrupted.
Knowing even slightly in advance what's coming gives you a much better chance of coping with it.
