This item makes for a good replacement for the once the player hits 70. This is because the Insignia has a five minute cooldown as opposed to the Medallion's two minute cooldown. Not only this, but the Medallion has resilience, which the Insignia does not. They both share a cooldown and so cannot be used together.
Though it is mostly aimed for PvP combat, it is useful for the Rage Winterchill and Archimonde fights in Mount Hyjal as both of these bosses have abilities which result in the player becoming frozen or feared. It is common for guilds to require this item for these bosses for this reason.
Technically there are 10 different versions of this item (one for each class), but they all have the same stats.