Taken from another site. If there's a group of mobs and you only want to fight one, follow these steps.
* Lay down a frost trap 1/2 to targets.
* Move to max range and initiate pull. Arcane shot is a good one for this method.
* Once mobs hit frost trap and are slowed, FD.
* Mob will now lose aggro and return to intial spots. On way back the first one hit is still aggro, the others are in 'evade' mode.
* Stand up before they get back and shoot intial mob. It comes back and since others are on 'evade', they return to positions and are not pulled.
* Viola! One mob from a chained link.