This is actually pretty useful even in non-tribal decks that happen to have a few elves.

Outside of my regular Elf deck, I also use it in a deck built around Undying creatures (like Flayer of the Hatebound) and Birthing Pod. I'll use the Harbingers almost as if they were a slightly slower Squadron Hawk to help fix my mana sometimes while giving me some 3 cmc creatures to sacrifice to the Pod if I need them. If not, I can always tutor for an Essence Warden to give me some life gain. Thanks to this card and Skyshroud Elf I can run a pure green mana base if I wanted to in a three color deck.