So you're saying...

/cast [pet:imp] Firebolt

Will have the pet instantly cast its firebolt...



Whereas:

/petattack

Will have a delay before it casts?



Either macro is spammed, so /petattack or /cast [pet:imp] Firebolt will be resent over and over.

On hunters, /petattack works perfectly; I'd assume it would work for a warlock too.