I have used it a couple of times when a ToD fire spell is cast. it reverses the timed fire spell and makes it as if it never happened. it only takes up one pip so whether you have ice mastery or are a ice wizard it matters not. if you got a pip available you can use it. just make sure to orchestrate it properly and cast it as soon as a ToD spell is cast on you or a fellow player. This spell comes with the fool's armor from the Hydra Hoard Pack.
Most damage over time (DoT) spells activate their damage over three rounds or three "ticks". Cooldown removes one of those "ticks" for all players on your team. Triage (the Life version), on the other hand, removes all the ticks.