I don't use it anymore because of TS but mine looked something like this.

#showtooltip Nature Swiftness
/cast Nature Swiftness
/cast Elemental Mastery
/use 13
/cast [target=focustarget] Chain Lightning

My nuke macro is now based around TS and looks like this:
#showtooltip Thunderstorm
/cast Elemental Mastery
/use 13
/cast Thunderstorm