In addition to its significant direct damage (which is instant cast and does not reset the shaman's melee attack), frost shock also snares the target. In PvE, it's useful against runners, slowing their retreat if the shock doesn't kill them outright. It can also be used for kiting high level mobs in certain raid situations. Against ranged opponents (in PvP, casters and hunters), the shaman can use this power to stay up close to use melee. Against melee classes like warriors and rogues, shamans use this ability to maintain their distance.