The Perfect Zone of Ultimate Safety is a term originated by Brian Clevinger in a blog entry. Beyond describing that pulling technique, the author makes an argument that Hunters are superior at pulling to all other classes.
Some pulls are very tricky, particularly if several mobs are patrolling on irregular patterns. The chance is high that the pull will bring unwanted adds. In such a situation, two abilities are helpful: A ranged instant pull, and the ability to abort the pull. The former is either a spell or a ranged weapon which has zero casting time, and instantly hits the target, the latter is an ability like Feign Death, Vanish or simply the discipline to die before other party members get on some mobs hate list.
Hunters are best suited for this type of pull. They do have an instant pull ability, they can drop out of combat at will (unless resisted), additionally they can apply some crowd control (like Frost Trap). A tank can grant the same measure of safety for the party, but only at the price of an increased repair bill.
In detail, when performing this type of pull the puller should move ahead of the party for at least 30 yards. The pull should be timed carefully, and after the first mob is hit, the puller needs to quickly decide whether only the desired mobs are aggroed (in which case he runs to the party), or whether the pull needs to be aborted (in which case he stays where he is and tries to dump aggro).
Meanwhile, the party stays back and waits - their position can be regarded as the "perfect zone of ultimate safety" , because if the puller does his job properly, and everyone else is fully aware of the plan, nothing will happen to them. This arrangement must be well planned and understood, or else the tank or healer might follow their natural instincts and draw aggro off the puller, or try to heal him.