If the wizard was broken wouldn't he have easily won gencon?
There are some concerns with the Wizard. The Wizards tower is very powerful, but it's a conjuration, and can easily be killed with a Force hammer or a force hammer and one, maybe 2 attacks by a creature or the mage.
I don't like that it's free to change spells, and you can do it every turn with no penalty.
The wizard is the most versitile, and has access to the most weapons at their dispposal.
There are a few other cards that need to be loked at and modified, but I don't know when that would hapen. Akiro's hammer, is a great one that needs to be fixed. It's currently garbage.
That's not how brokenness works. If it's significantly easier to win with the wizard than the other mages, or if other builds have to go out of their way to prevent the wizard in particular from having that advantage, then the wizard is broken, even if he doesn't actually get first place in Gen Con. In mage wars player skill plays a bigger role in who wins than spellbook building.
Similarly, if it's so overpowered that it restricts design space for future cards or future mages (e.g. alternate Wizard), then a fix might be warranted. I fear that's maybe one of the reasons why we haven't seen Water spells that deal Frost damage yet. If there were Water attack spells on the same power level as Fire, Air and Earth, especially if they have some sort of freeze effect (hence "Defrost" keyword on some flame damage cards), then a Water Wizard - who already benefits from cheap Dissolves and Acid Balls - might be too strong.
Regarding Wizard's Tower, I'm always surprised it isn't Zone Exclusive. Most corporeal conjurations that represent large objects are Zone Exclusive... and surely the Battle Forge represents an object small enough to fit inside a single room in the Wizard's Tower. Yet, you can put a Wizard's Tower in the same zone as another key conjuration (like a Battle Forge). Compare to the Warlord's "outposts" that can't even be placed in adjacent zones! And free spell swapping is pretty crazy when you consider the usual spellbind swapping costs or restrictions on wands, Thoughtspores, etc.
Last night I played an Earth Wizard only because we earned story achievement points for casting attack spells and both my Warlock spell books were lent out. I briefly considered a Thoughtspore-swarm Forcemaster, but glad I didn't because another player went with exactly that.
In one of my matches, my Wizard's Tower proved to be a liability because its Hurl Boulder got Reverse Attacked for 7 self-inflicted damage (doh! should have Seeking Dispeled first). But in the other, it pulled off a free Hurl Rock to crush an Anvil Throne Crossbowman immediately after Huginn had Teleported him off of his Archer's Watchtower from behind a wall. Later, the Tower Hurled a free Boulder at the opposing mage on the final turn right after his armor had been stripped. As for Huginn, in addition to Teleporting without LoS restrictions (due to flying), he also casted an Earthquake that took out a wall and Battle Forge, and was about to Explode some armor when he failed to avoid a Hurled Rock (splat). Huginn can be a pesky threat that just adds another option each turn through additional planning, resulting in some big plays that generally only a Wizard can pull off. If he had Spellbind, he'd be way too good - but I had Dispel bound to a Mage Wand, Hurl Rock bound to an Elemental Wand, and either Rock or Boulder bound to the Wizard's Tower at any given time, so it didn't bother me too much to have Huginn burning a Teleport or Dissolve or Explode or Earthquake or... whatever each round.
We can debate whether or not each particular "Wizard only" and "Arcane Mage only" spells are overpowered compared to options available to other mages, and whether or not the current Wizard mage's abilities are too good in comparison (e.g. don't need to be built around like most of the other mage's abilities), and I'm sure there will be many pros/cons listed and many people taking the for/against sides. But as Schwenkgott noted, my proposed change doesn't errata any cards nor take away any abilities; it simply reduces the options during spell book building, limiting the number of answers (and threats, in the case of Grizzly-based Wizards) that the Wizard can bring, so he isn't as stocked full of answers. That said, he still has the cheapest access to Dispels and Teleports, both spellbind Wands, all the key channeling increasers (Crystals, Harmonize, Moonglow Amulet), most of the mana denial spells (Mordok's Obelisk, Essence Drain, Suppression Cloak - although he might be paying triple for Suppression Orb), etc... so I don't think this proposed change would make him unplayable. And all it would involve is errata to his ability card.