I also just got a 2 Legendary Arena run! So far it's gone 3-0. This is what I drafted from memory (I have not setup Arena Mastery yet, but I think I am about to). I clearly forgot a few cards, but I think they're probably average 2 or 3 drop minions. (Edit: Actually I recounted and apparently I remember all 30 cards which shocks me that my memory is so good, there's possibly 1 or 2 errors, but this is very close to the exact draft). Where I remember the draft cards I rejected I've put the cards I didn't pick in ()s.
1s:
2 x Mana Wyrm
2 x Arcane Missiles
1 x Undertaker (Silverback Patriarch, Mogushan Warden)
2s:
1 x Sorceror's Apprentice
3 x Frostbolt!
1 x Novice Inventor
2 x Amani Berserker
1 x River Croc
3s:
1 x Dancing Sword
1 x Tauren Warrior
1 x Arcane Intellect
1 x Duplicate
1 x Scarlet Crusader
4s:
2 x Polymorph
2 x Violet Teacher!
1 x Cone of Cold
5+s:
1 x Stranglethorn Tiger
1 x Frost Elemental
1 x Sunfury Protector
1 x Black Knight (Tinkmaster, Alexandria)
1 x Flamestrike
1 x Ysera (Loatheb, Hogger)
1 x Molten Giant (Sea Giant, Big Game Hunter)
On Tauren Warrior: I agree that it's pretty garbage with most classes, but in Mage it's probably only a slightly below average 3 drop since you can activate it yourself. An expensive Amani Berserker with Taunt is better than a lot of things in a Mage deck.
On Undertaker: There is definitely only 1 card with Deathrattle in my deck (Dancing Sword) but it's still better than Silverback and Mogushan.
On Black Knight: I briefly debated taking Alexandria, but eventually decided on Black Knight because of the popularity of Taunt cards in Arena. I haven't actually drawn him yet, but I'm sure he'll be great. (I never considered taking Tinkmaster.)
On Ysera: I really considered Loatheb here, but I think he's better in Constructed than Arena as Arena decks tend to be more minion heavy (not the one I drafted, but in general). Ysera on the other hand can generate a big card advantage late game and hopefully by the time she's played some other beefy card has eaten the creature removal spells from the opponents deck. (This happened in my second game where Protector ate a Polymorph letting me put Ysera out safely and win.) I like Hogger, but he's usually killed off before you can get much value out of him, Ysera and Loatheb are superior in my opinion.
On Molten Giant decision: This was my first choice in the game and in retrospect I would have taken Sea Giant. There's been plenty of opportunities to play it for 6 or less (the Violet Teachers have been spawning lots of Apprentices and Duplicate tends to let you flood the board at some point, especially if you duplicate something cheap or a Violet Teacher). I considered taking BGH, but thought to myself "Would I rather kill a big creature an opponent might have or have a big creature that an opponent might kill?" The answer was then clear that I needed a Giant. Luckily I drafted other ways to deal with large threats.
On Violet Teachers: Normally I would consider this a pretty average card, not bad, but not great. In this draft though they get a lot of value almost always creating 1 or 2 apprentices before eating a silence or being killed.
On the deck in general:
This is a spell heavy draft. Two Mana Wyrms, two Violet Teachers and a Sorceror's Apprentice synergize really well with spells. Lots of Frostbolts, two Polymorphs, and a Flamestrike are great on their own, but having those spell synergy minions makes Arcane Missiles, Arcane Intellect and Cone of Cold punch above their weight class. No opportunities to draft Spell Power cards made me sad, though, and I think would have really pushed this draft through the roof.
This deck has a lack of strong 4 drops (no Yetis, Water Elementals or Senjins were seen in the draft, nor were any Fireballs), but a lot of the smaller cards can trade up so they're making up for it a bit.