if you can live with actual targetting the mob you shoot and you are using an ftl i would use the following:

Code:
/click ActionButtonX
/castsequence  reset=target/combat Flame Shock, Lava Burst, Lightning Bolt, Lightning Bolt, Lightning Bolt, Lava Burst, Lightning Bolt, Lightning Bolt, Lightning Bolt
with the ftl-assist-macro (/assist [mod:alt,mod:ctrl ..... ) bound on an Actionbutton.
You can fnd this in the wiki, on 'using /castsequences ' and 'Shorten macrospace / simplify group changes '