From Dual-Boxing Wiki

Description

Whenever a new target is selected, a Scorch is cast from the first cast sequence. Then the second cast sequence becomes in active until a new target is selected. The second cast sequence keeps Scorch active and rotates between the different spells to trigger different buffs/debuffs.

The fast casts are put in front and longer ones are in the back, which allows you to kill non-elites quickly.

Macro

/castsequence [nomod] reset=target Scorch, nil
/castsequence [nomod] reset=6/target Scorch, Fire Blast, Frostfire Bolt, Fireball, Pyroblast

Extension

Add this to the macro to add multi-target DPS when a modifier is pressed:

/castsequence [mod] reset=12 Living Bomb,nil