This is one item that tends to create confusion among players.
Stops target dead in it's tracks while inflicting an amount of dd when it first hits the mob.
When dd spells or melee damage reaches a certain point, root breaks.
When the mob is low on health, it will continue fighting.
It slows down the mob immediately making it very easy to keep up with fighting.
When the mob is low on health, the mob will turn and try to run, but can't go anywhere. At this point, there is no more damage coming from the mob.
Although snare can be used anytime during the battle, it is best to cast it when the mob is between 30% to 40% health. This SHOULD stop the mob long enough to finish it.