Nice to see someone come back after a break!

So first off, I am planning on getting Academy. I think it would be a nice stepping stone before I get people into Arena. I am planning on starting with the strater initially, to get a feel for it, but was wondering what people thought of the expansions. Which ones are the most fun to play, and which ones have cards that are specially good for Arena?

I really enjoy academy both as a quick pseudo-mage wars game and as an introduction, although I don't like it nearly as much as the real goods. Still, it's a very fun, quick game for when mage wars arena is just too much.

Every academy expansions contains some very nice arena cards for their respective arena counterparts. Not every single card is useful in arena, but many of them are. Some are even game changers. You should check them out.

What is the general consensus on Domination. Is it a good alternate game mode?

Personally not a fan of this mode. I know other people do enjoy it.

Obviously getting Paladin vs Siren.

You should! Great expansion!

Also heard snippets about Lost Grimoire. Is this a collection of promos from before, or is it akin the the core spell tome, or just new spells not coming with Mages?

It's a combination between old promo's and new spells (without mages) There are no existing spells in the set.

Is there news on things to come? Like a forged in fire esque set for forcemaster/wizard?

Apart from Academy warlord and Academy forcemaster: No.

Regarding packs, how is the card distribution. I remember buying 2 copies of the core set, and I think 2 copies of Forcemaster/Warlord in order to have enough copies of spells. Are the sets including 6x level ones and 4x level 2? or is 2 sets the go to? Are the card lists posted somewhere? I remember there used to be a checklist of sorts, but I cant seem to find it through my brief perusal of the site.

I believe a rule of thumb for number of spells in a set:
Level 1: 3x
Higher level: 2x
Epic/mage only: 1x

Might not always be correct.

Regarding errata. There was 3 cards errata'd when I was playing, Hand of Bim Shalla, and 2 others that I forget. Has there been any other errata's (I think i saw something about Wizard?) Where can you find the errata and is there some way to get the errata'd cards?

There are probably some rewordings but nothing major apart from the wizard and the wizard tower.

Finally regarding promos. Is the policy still that every promo will eventually be released in a set? I also saw mention of alternate art cards for Paladin and Siren if you preordered. Does that mean they wont have an alternate Mage in the future? Are these cards still available?

Still the same policy! No idea if the alternate art is available.

Pretty interesting book. Very hard though to tell if it's viable or not. My guess is that you do rely on the element of surprise. 

The main thing that's really strange is the choice of a priestess. Since you are going for the short/mid game you probably won't win in the long run. Her abilities won't really support you a lot. I think the Anvil throne warlord would be my pick with all the equipment and runes. You could bind an attack spell on an elemental wand with the discount rune. You would also save a lot of spellbookpoints for all the earth spells. Once academy is released, warlord would be an even better choice with gear up and the other new equipments. If you really want a 10 channeling mage, I'd pick the wizard since he has air training and has supporting abilities. (A cheap short range attack spell, a shield and maybe wizard tower)

Some comments on the card selection:
Radiant breastplate: You want to keep your distance and stay away, thus you could probably use a different armor without that ability. (Asyran robes or elemental armor)
Mohktari: I don't think it really supports your game plan. It's expensive and works better over time.
Dragon's breath: It's a cool spell, but you probably will focus on the mage. I think it's better to use more meteorites or thunderbolts. I also think you need more attack spells in general. (level 1 & 2)

I've never seen this card being used. 4 spellbookpoints and the extra cost make it very expensive.. Still, pretty cool you managed to make it work in a game!

(Second chance from priestess academy does it better though imo)

In my point of view we only have 3 'pets' out of 14 mages. The holy avenger, the blood reaper and the bm pet. Each with their own flavor and mechanics. Pet is a simple big boost especially when fighting along the bm, avenger grants extra life an a revenge attack and bloodreaper gives bloodthirsty and heals the warlock. I dont see how 3 slightly similar abilities are an issue.

The newer familiars/spawnpoints are quite different. (naiya, cassiel, banner, echo) and libro is also quite unique.

Are you saying that the newer cards are better or the older ones are?

No.

http://www.arcanewonders.com/game/royals/

You are missing [mwcard=MW1C26]Necropian Vampiress[/mwcard]. The one I see most is her, the grizzly and bridge troll. Personally I'm pretty sure I'll stay in school once academy is released. I don't like spending 12+ spellbookpoints on a creature. 

You know, religious people often have a book. (Bible, Qur'an) It doesn't have to be a magic book. He might as well quote phrases to his opponents while burning them. Condemning them to hell.

Also, not every equipment on mage art is going to be released.