Harbinger is a powerful avatar and I'm on a mission to prove it!

@dendros mostly built the deck and already demonstrated a solid theory behind it: You have a high percentage chance of rolling at least one square you can leverage to your advantage, taking luck partly out of the equation (although feel-bad rolls will still happen).

Here's some strengths that mean Harbinger shouldn't be dismissed:

Strong starts

Playing a turn ahead of your opponent is powerful. The reason mana ramp like cores and stone aren't played is the card disadvantage / dead draws and Harbinger doesn't have that. You get a boost from turn 1 for voidwalk minions and it can be enough to overrun the opponent. Besides voidwalkers, the deck plays above-rate earth minions that can be backbreaking if they sneak out a turn earlier.

Aggressive positioning

This one depends partially on your rolls, but in general the slew of voidwalkers you play are great at getting up in the opponent's face and dodging those pesky defensive sites, all while being immune to removal the turn before attacking.

Big finish

The combination of air-based ramp with harbinger's discount means you can reliably drop even the fattest minions already in the midgame. Combined with things like whirling blades and grapple shot, they're sure to dominate the board and can mean a swift demise for your opponent. Finally, air means you have plenty of ways to finish the game, from the classic toolbox'd Zap! to Bolts and Earthquakes.

All that combined is a potent mix and you should give this avatar a whirl!