So, have we all not wanted to find a way to effectively use this spell? Well, I have the basics for a macro that i think might help. This macro will target the closest target and cast ESF, then the second click will target another target not targeted and cast the second if needed. Keep in mind that since technically this is an aura and not a spell and contains commas in the name, I am not sure how to use it as a cast sequence, so you just have to wait one second to cast the second. Also to cancel ESF tap it again for each one you have out. This is working for me well on targeting dummies, test it and lets see how it works out.
#showtooltip Storm, Earth, and Fire
/targetenemy [noharm,nodead]
/focus [nodead]
/targetenemy [nodead]
/cleartarget [dead]
/clearfocus [dead]
/cast [harm,exists] storm, earth, and fire
/cancelaura [noexists] Storm, Earth, and Fire