Yeah. There's a ton of different ways that it could be done, and none of them perfect. As a measure of popularity, this is the one that probably makes the most sense.
But you could definitely thumb the scale in different ways by breaking the selection down even further and splitting the bracket into four different groups, although like with Arizona State ending up in the "East" bracket you'll have some weirdness either way.
You could go by Class Group:
Warriors (Fighter, Warlord, Barbarian, Swordmage)
Priests (Cleric, Druid, Paladin, Psion)
Rogues (Rogue, Bard, Monk, Ranger)
Wizards (Wizard, Sorcerer, Warlock, Artificer)
Or by age, if you wanted a "one main-4 to rule them all" free-for-all early on
OD&D (Fighter, Rogue, Wizard, Cleric)
AD&D (Ranger, Paladin, Druid, Bard)
3.X (Monk, Barbarian, Sorcerer, Artificer)
4e (Warlord, Warlock, Swordmage, Psion)
Or by 4e-style Power Sources
Martial (Fighter, Warlord, Ranger, Rogue)
Arcane (Wizard, Warlock, Sorcerer, Bard)
Divine/Nature (Cleric, Paladin, Druid, Barbarian)
Psionic/Wild Card (Psion, Monk, Artificer, Swordmage)
But again, I think splitting the group in half and ranking them based on their overall popularity is as fine as any. Besides, while Rogue and Wizard might be sitting pretty at 1/3 of the vote, you never know if enough people might show up to say "to hell with these boring OG classes!" and vote for Barbarian or Ps-... ...whichever wins the Artificer/Bar... ...Warlock