Actually, I don't know why I didn't think of this before, but
@
The Dewk
schooled the Utah scene at our latest January Monthly with an all hero army (though it should be noted that 4/5 of the heroes was C3V/SoV):
The Varja
Asterios
Kaemon Awa
Rygarn
Bol
I think in the long run it's very possible to do well and even win a tournament with an all Unique Hero army, but it's going to require some incredible play. The Dewk, for example, is a great player and definitely has the skill level required to pilot such an army to success.