I disagree. I am convinced that Sardonyx is not tournament viable irrespective of arcane support. Yes, you can overcome many of the things that neutralize him using arcane cards, but that doesn't matter. Not in his case. The issue is that he costs too much for how much damage he does, and he's the worst creature defensively in the game, particularly when you consider that he kills his controller with a stronger version of Ghoul Rot.

Congratulations on your win.

Here is my analysis of your spellbook. I have thought about it a fair amount, but never actually playing against it. Let me know what you agree and disagree with.

I don't think Gate to Voltari really gives you as much late game strength in this book as you claim simply because you don't run a strong enough set of creatures for a truly dominating late game. If someone kills both of your Wizard's Towers, a big part of your tactical advantage goes away, and a stronger set of creatures could overwhelm you. I'm sure overcoming your economic and action advantage in the short term is difficult, particularly given how mana efficient the stats on Gate to Voltari and Wizard's Tower are, but I still think you're overstating your late game strength. I would describe your spellbook as trying to reach the midgame very quickly, and then extend that midgame as long as possible while building an insurmountable tempo/action advantage, and preventing your opponent from building the investments they need to reach a strong late game position.

I also think you are overstating the advantage of Jinx, though I will freely admit that I underestimated it. The thing that makes it such a key card in your spellbook is the combination of the action economy you build with your familiars and spawnpoint, your efforts to gain a channeling advantage, and your reliance on attack spells as your primary source of damage. If you don't have an action and a channeling advantage, the advantage Jinx offers you is much smaller. You're paying 3 mana to reduce the number of quick actions available to you and your opponent by 1, which is mostly worthwhile when you have an action and channeling advantage, or a large enough board advantage that being behind on mana is acceptable to press your advantage. It gives you an overwhelming advantage against mages that don’t increase their action economy at all, but against someone with a similar action/mana economy, it’s significantly less valuable.

Because your primary damage source is attack spells, Jinx gives you a significant advantage in reducing your opponent's ability to defend against your attacks. Acid Ball in conjunction with Dispel/Dissolve for things giving defenses makes it very hard to defend against attack spell spam if your opponent has a significant action advantage, which Jinx helps you to exacerbate. For someone that relies primarily on creatures for damage, Jinx will tend to be weaker in general (unless they have their opponent locked down in a position of massive tactical inferiority), since their opponent can play a wide variety of creatures to guard and attack those creatures. They could also try to avoid those creatures until their opponent runs out of Jinxes. It still has applications, but it's easier for a wider range of opponents to deal with it.

Against the kind of attack spell spam you focus on, the best answer is intercept creatures that cannot be efficiently destroyed with attack spells. The Priestess is also much less vulnerable to Acid Ball weakening her defenses. Overall I think the Priestess has one of the better matchups against this strategy for those reasons combined with her potential for a really strong late game.

Why do you think that the Pentagram is the best creature spawnpoint besides Gate to Voltari? I like the consistency that the Lair offers considerably better, particularly given how much better it in terms of action economy to play turn 1. There are good dark living creatures, just not good ones to support a spawnpoint play. I feel like Infernian Scourger was printed to try to fill that role, but he’s just not nearly good enough at it.

I agree that for competitive play, Sardonyx is the worst card in the game.

The card that I am most excited about from Academy so far is Fang of the First Moon. It gives a BM swarm build a much stronger followup.

In terms of the enchantments, I'm not expecting much from Iguana Regrowth. Most creatures small enough for the cost to not be prohibitive don't have that much armor, and for large creatures I prefer stronger sources of healing anyway. I may use it in Academy, but I don't see myself using it much in Arena.

Gator Toughness is much more interesting to me. It gives us a way to make a small or medium sized creature significantly harder to kill, and provides a nice middle ground between Bull Endurance and Rhino Hide. It should also be good on larger creatures, but I'm particularly intrigued by how much better it looks for small creatures than previous enchantments doing similar things. I can see it being a solid choice on Fellella or Huginn.

I wonder whether Wychwood Faerie will be worth the full action in Arena.

For the opening for the Bear Master, I'm thinking:

Turn 1 (19): Ring of Beasts -> Steelclaw Matriarch (7)
Turn 2 (16): Enchanter's Ring -> Steelclaw Matriarch (4)
Turn 3 (13): FD Brace Yourself -> Steelclaw Matriarch (2)
Turn 4 (11): FD Bear Strength -> Steelclaw Matriarch (0)
Turn 5 (9): Bearskin -> Steelclaw Cub (0)

What do you think? Does it get enough bears out fast enough? My thinking is that you play a bear per round through round 10, then you play a Steelclaw Grizzly every other round. That should carry you through round 18, and if you haven't won by then, you've done something wrong. 

I like the first one a little bit better in terms of creature selection, but I like the enchantment selection a little bit better in the second book, though it would be too much for the 1st book.

Overall, there are a few suggestions I have:

Eagleclaw Boots are good, but I would actually stick with Leather Boots for a Priestess with Veteran's Belt.

Similarly, I would consider running a Rhino Hide as another source of armor for your mage.

I would run a Bear Strength for Brogan in the first list.

For the first list in particular, I don't think you need that many Nullifies. You aren't relying on a single massive threat, you're playing multiple threats, which means that Nullify shouldn't be that important for you. Having 1 or 2 is probably enough, and I think you could get away without any. For the second list Nullify makes a bit more sense, since you are building up just a few creatures to be huge monsters, and losing an action with one of those creatures is a much bigger deal.

In the second list, I would consider Lay Hands.

What were you thinking in terms of the opening? Something like:

Turn 1 (20): Asyran Cleric -> Battle Forge (7)
Turn 2 (17): D Meditation Amulet -> Meditate -> Temple of Asyra -> Mana on Temple (7) [1]
Turn 3 (17) [2]: D Enchanter's Ring -> D Guardian Angel -> Meditate -> FD Rhino Hide -> Mana on Temple ( [1]

Puts you in a pretty strong position and is reasonably flexible in the face of aggression. It's pretty similar to my Anvil Throne Warlord opening. You can substitute another creature for round 3. Brogan gives you a strong offensive threat, another Asyran Cleric gives you an even stronger economy, and Guardian Angel is a strong defensive play. If you are worried about a strong attack in round 2, such as double Hurl Boulder, you can just deploy Dragonscale Hauberk and play the Temple of Asyra or Guardian Angel, depending on how worried you are about aggression. You'll be a little behind in economy, but something like that puts you in a much stronger position against a fast attack.

The reason Reverse Attack doesn't work against the attack from Explode is that Explode is unavoidable. You reveal the Reverse Attack in the avoid attack step, but it is simply discarded without effect at that time due to the attack from Explode being unavoidable. It doesn't matter that it is not an attack spell. Block works just fine against Burst of Thorns. Reverse Attack is less efficient against Burst of Thorns, but it still functions.

I've tried a few times to use Staff of Beasts, but ultimately came to the conclusion that it was just not a good option. The Johktari Hunting Knife looks like a much better deal. It's more action efficient, it costs less, and while it puts some constraints on activation order, it's an efficient means of boosting damage output, whether with a swarm or with a few bigger creatures. It works well with creatures that are guarding, and combos particularly well with Defend. I'll probably be switching my Straywood Beastmaster's weapon out for this when I get my hands on Academy.