The saved action is quite important to this build. As is the free mana.
This above is an idea build I'm doing some refinement to it. After the last tournament it played at.
I guess the question is whether or not it's worth it.
If you put Harmonize on your Gate on turn 1, you're paying 2 quick actions (although one might as well have been full) and 18 mana, looking to save 4 full actions and ... an amount of mana that depends on how many spells your opponent casts and how many rounds it takes you to get your 4 Harpies in play. Are you willing to wait, say, 7 rounds to get your 4th Harpy? And beyond that, any mana that the Gate channels/collects is wasted.
If set on Gate to Voltari, I'd probably include (at least) 1 more really expensive creature so that, if your opponent weathers the 4 Harpies for a few rounds, you at least have something to spend that mana on. Could be a Hydra or Jelly or Gorgon Archer. Has to be "Corporeal Arcane" so those are really the only big, scary, expensive options that can be deployed by the Gate. Or maybe Huginn for support, as he can see over walls, and can cast whatever Incantation is useful to free your Harpies (e.g. Teleport or Dispel or Heal or whatever) in case they need help.