Going back to Laddinface's original request, I think we should be focusing on trying to invent cards that would bring all of the other classes up, rather than errataing/nerfing the Wizard.  Certainly Arcane Wonders can errata the stat card if they chose, but it's a pretty extreme response.

Beyond that, I don't even think that adding an "enemy" school to the Wizard would be significant.  Most Wizard books I have seen have around 3-5 SP of spells from either the War or Nature School.  Sure, 5 SP aren't trivial, but is it worth card errata to only achieve that?

No, I think as everyone has pointed out here, the Wizard became excellent due to the printing of Wizard's Tower and strong Arcane and Elemental creatures.  He used to bumble along with the rest of the base set mages.  I think the trick is to make the other mages excellent through similar means.  (And I would argue that the Druid is already on par with the Wizard.)  Let the presses print more excellent War, Light, Unholy, Fire, Water, and Air spells.  (I leave out Nature, since it's already really buff.)  Sure, elemental spells also benefit the Wizard, but he already has a bunch of plum choices.  It's diminishing returns for him to get access to more things that are already of equivalent power.

I think that's where we the players come in.  What do the other mages need to do to wow us?

Thanks to Charmyna for starting this thread, and Deckbuilder for his organizational efforts.  My first contribution is on the subject of Dissolve/Dispel:

Bleeding the Color Wheel
I come from a Magic: the Gathering background, so I'm going to talk in language that is familiar with me.  Mark Rosewater (Magic's lead designer) has written some pretty good articles (https://www.wizards.com/magic/magazine/article.aspx?x=mtgcom/daily/mr85) about the value of color identity.  The idea of an identity is pretty important to the schools of Mage Wars as well.  I think it is important to be cautious about bleeding an effect in to too many schools, lest all the schools become too similar.  (I think the folks who are angry about Damnation being color shifted into black are right to be, in changed the color balance forever.)

That said, I think part of the reason the Wizard is so good is that there is a lot of pressure to place many copies of Dissolve and Dispel in their books, as well as probably a few Teleport and a Nullify.   In particular Dissolve and Dispel are needed because there are so many cool equipment and enchantments in the game.  They are sort of so good that everyone needs to destroy them.  Right now in every book I build I place at least 3 of each of these, even if I must pay an out of school cost.  The Wizard (especially a water wizard) gets a huge savings on spell points by being able to buy both in school.  Likewise, part of the great weakness of the Warlord is that he must pay enemy school costs for Dispel!

At the very least I would like to see one non-Arcane Dispel to help the Warlord.  As I suspect some Mage in the future will have Water as an enemy school, I think by that time there should also be a non-Water Dissolve.  I don't mean some version with a twist, I want a bread and butter boring card for card equivalent.  I have made Nature mages and Fire mages, and though I often have a copy of Corrosive Orchid or Explode, I still have multiple copies of Dissolve because often I don't have the extra mana to pay for the flower or the fire.

If our goal is to specifically bring the other mages up to the Wizard's level, a novice version of Dispel and Dissolve would be an effective step.  I think these are good candidates because they represent a universal magic effect that everyone uses, and therefore it feels okay from a flavor perspective.  The functional effect is that now everyone else gets an effective +4-8 SB points because they are no longer paying double for their pile of Dissolve and Dispel effects.  This *is* power creep, in the sense that we are making access to these effects forever cheaper in terms of book points.  It would be less power creep if only one of these spells were made Novice.  I'd choose Dispel, since it could be easily powered down to range 0-1, and wouldn't help the Wizard while helping everyone else, and gives the Warlord 2x help.

I wonder if there are more flavorful ways of giving non-Water or non-Arcane tools to destroy equipment or enchantments?
* War creatures/ equipment/ command/ attack with a new Shatter effect, which destroys equipment?  (rough for expensive equipment, though Forcemaster has lots of Defense effects to counteract it)
* An Unholy Curse/conjuration that deals damage to target/radius/entire arena for each equipment or enchantment active on it.  (Two different spells, one for enchants, one for equipment.)
* A holy enchantment (Mage only?) that gives mage armor = enemy mage's armor.  ("Share Strength")

Of all the approaches, I find these last most interesting.  I want the spell schools to each have their own distinct flavor, but they *all* need ways to deal with equipment and enchantments.  Until they have effective ones, they are going to have to keep having a SP deficit relative to the Wizard by buying the same old stuff out of school.

Circle of Fire:  I actually think this is one of the most important spells in the game.  I think without considering interaction from an opponent, level 1 creature swarm falls just behind wall of thorns + push in how quickly you can kill an opponent clocking in easily on turn 4.  (Wall push kills on turn 3.)  Circle of Fire is by far the best way to kill a swarm of Hawks or Foxes, and as such is a spell I'm always thinking about splashing as a "silver bullet" for that kind of opponent.  In the new druid metagame, I suspect it also offers some opportunities for real coups against plant pits.

Banish: This card seems too expensive to me for what it does. Remove a creature for 3 turns only to have it return unscathed for 14 mana? Why not summon my own strong creature with that mana, or do something else?

I think it's right to compare this spell to Turn to Stone, Force Hold, and/or Sleep.  It's a spell designed to neutralize a big for a while so you can do something without it bothering you.  On the front end 14 is a tremendous amount of mana.  Turn to Stone for 3 turns costs 14 as well, Force Hold for 3 turns costs 10, and Sleep 7/9/11 on level 4/5/6.  I think a premium is being paid since Banish works on anything.  That said, I'm not generally willing to pay for Turn to Stone, and Force Hold isn't my thing either.  I like Sleep more since it is so cheap, *and* requires some kind of resource expenditure from my opponent to end it.  I guess if level 6 nonliving summons started to be a big thing, I might consider a Banish?  But until then, it shall remain forlorn.

I am going to use a 5 point scale to classify spells in Mage Wars.  Rather than try to rank them (which I think is not useful), I just want to score them as a thought exercise.  I am leaving out most specific mage only spells, since those don't feel relevant to rate.  Here is my scale:

5 - I almost always put one or more copies of this spell in my books regardless of school.
4 - I strongly consider putting this spell in my book regardless of school.
3 - I almost always put one or more copies of this spell in my book if its in my school, and rarely would splash it.
2 - I sometimes put this spell in my book if its in my school.
1 - I have trouble imagining using this spell, even if its in my school.

5s:
Teleport
Dispel
Dissolve
Eagleclaw Boots

4s:
Steelclaw Grizzly
Mana Crystal
Mana Flower
Battleforge
Dragonscale Hauberk
Veterans Belt
Regrowth Belt
Meditation Amulet
Regrowth
Rhino Hide
Harmonize
Cheetah Speed
Nullify
Sleep
Maim Wings
Acid Ball
Hurl Boulder
Heal
Minor Heal
Purify
Wand of Healing
Dispel Wand
Mage Wand

3s:
Leather Gloves (counts as being in everyone's book due to Novice)
(any armor granting equipment not listed elsewhere)
Dancing Scimitar
Suppression Robe
Lair
Gate to Voltari
Librum Mortus
Temple of Asyra
Archer's Watchtower
Grimson Deadeye
Sir Corazin, Blademaster
Goblin Slinger
Knight of Westlock
Royal Archer
Galador, Protector of Straywood
Karalathor, the Devourer
Wall of Thorns
Zombie Brute or Skeleton Warrior
Shaggoth-Zora or Mort
Undead Archer
Necropian Vampiress
Devouring Ooze
Gorgon Archer
Whirling Spirit
Iron Golem
Force Push
Force Wave
Precise Strike
Piercing Strike
Power Strike
Piercing Shot
Mind Control
Turn to Stone
Force Hold
Fortified Position
Sacred Ground
Enchantment Transfusion
Bear Strength
Bull Endurance
Eagle Wings
Mongoose Agility
Falcon Precision
Healing Charm
Block
Decoy
Purge Magic
Seeking Dispel
Ghoul Rot
Drain Life
Magebane
Poisoned Blood
Agony
Enfeeble
Idol of Pestilence
Deathlock
Suppression Orb
Mordok's Obelisk
Ring of Fire
Fireball
Fireblast
Chain Lightning
Jet Stream
Geyser
Zombie Frenzy or Reassemble

2s:
(any non-armor spell not listed elsewhere)

1s:
Stumble

Curious what other people think?  Should some spells be rated higher?  Lower?  Are the categories useful?  Have I described them well enough?

@DeckBuilder:  I am glad you found my observations to be useful.  I am also delighted that you have found that the great wheel of the metagame spins ever forward.  The druid book from your testing looks brutally efficient! 

Glad to hear you had some fun games with the BB!
Its easy to say afterwards but I always thought Druid is the best candidate to beat BB. Treebond and Barkskin are awesome to help surive BBs blast. Summoning plants with the Vine Trees action on top of conjurations is great too as well as using Tanglevine and stuck markers on the BB to make him use his teleports. Maybe even more important are the cheap Dissolves+Acid Balls and the great in school heavy hitter (Grizzly).
I feel its time to say it again! Its (almost) all about spellpoints! What makes the BB such a successful build IMO is that his main strategy heavily depends on in school spells and the build does not need any level two or higher out of school spells (in the latest iteration I removed Dancing Scimitar). This allows the BB to have 2-3 copies of the most important spells and still be flexible enough to adjust to many different builds.
The Druid is such a formidable opponent against the BB since he is very spellpoint efficient as well! He can include many Acid Balls, Dissolves and Dispels needed to beat BB and still have enough spellpoints left for a couple medium/big in school creatures and many in school enchants to be well suited against other builds than the BB.

@Suppression Orb:
Im sure it will work great with this build but I dont want to spend too many spellpoints for stuff only useful against multi creature mages. If I play against a solo mage all the spellpoints put into Obelisk, Essence Drain and Suppression Orb will be useless in that game. Anyway, if I accept to spend four more Spellpoints into stuff only useful against creature builds, I would prefer two Essence Drain over Obelisk since I guess in the majority of situations they will cost him more mana than the Obelisk. Even if he dispels them, he will have lost 2-3 mana compared to what I invested and that dispel wont be used against BBs valuable Regrowth/Rhino Hide later.
You mentioned Siphon. I can see that spell is very useful for the BB and it works against all mages (not only creature builds). So I will test it out soon. Thx for that advice!
Btw I removed the bat .

@Charmyna:  1) A point of curiosity: Did the Philosophy of Fire post contribute to the shaping of the BB book?  If so, I'm curious about your thoughts on the subject.  (Either here or there, as appropriate.)

2) I think it might be best to accept a few SB points that are "worthless" against one kind of book and "amazing" against another book, rather than a book full of "medium" quality spells that work everywhere.  I have found in most matches I only use the same 80-90 points worth of spells.  To me, this means I should be spending the other 30-40 points on "silver bullets" to gain great advantage in the right circumstances, or to help with a big problem with my book.

I recognize that if your book is more "controlling", or relies on "attrition" or a long game, you will need to use more of your SB points over the course of the match.  So, maybe for the style of book you seem to play, you might regularly use the same 100-120 points in a single match as opposed to the 80-90 in the styles I have been playing.  Even so, perhaps even as few as 10 points of silver bullets might be very helpful?

3) I completely agree that the Druid is the natural (*har* *har*) counter to any solo build.  Between Barkskin and her tree, she can get so much more regeneration and armor relative to all the other characters that attacking her life total is highly ineffective.  If mage assassination isn't an available path to victory, the game must become one of attrition.  With a great spawnpoint, and a range of spell training that allows a full and flexible book, she is very good at attrition.  My current opinion is that she vies with the Wizard for the title of best mage, and I think it's very close between the two.  (It has a lot to do with Arcane and Nature having most of the best cards split between them, but also with strong stat cards and class-only cards.)

"maybe with an increase in Purify running around I'm on the wrong side of the armor game."

Just an FYI, corrode is an acid counter, not poison so purify doesn't remove it. Only priestess, healing wand, spring of renewal and swapping armor can remove corrode.

Ahh, excellent.  Thanks.  Corrode forever!   

With gust-o?

LOL.  I wish I could give you gold, or whatever these "Banana Sticker" things I see are.  Perfect answer.