/target NPC works fine, but you can shorten your macro quite a bit.
Code:
/tar [dead][noexists] Shakes O'Breen
/tar [dead][noexists] First Mate Nilzlix
/tar [dead][noexists] Captain Steelgut
/tar [dead][noexists] Doctor Draxlegauge
/tar [dead][noexists] Deckhand Moishe
/cast [harm] Fel Flame