Patches, please.
I hit the gold cap (30 wins in one day for 100 gold/10 gold for every 3 wins) for the first time, ever. And I did it in two hours playing Patches Hunter in this All-Star Squad Brawl. It's ridiculously quick, since someone concedes almost immediately in most matchups.
The only two, true hard-counters that I played were Ice Block Mage (this is unwinnable) and an opponent playing Patches who got to go first. Going first with Patches is almost always an auto-win, especially in the mirror match.
In my 30 wins, I did scrape together victories (and some losses, of course) against supposed counters: Armorsmith Warrior, Power Word Glory Priest, Maelstrom Portal Shaman, and Unstable Ghoul Warrior (the latter is actually not a good counter, and I never lost to it).