From mage cards,
Effigy is perfectly playable and decent. Ideal openings would be mad scientist turn 2, which dies then turn 3 play a Shredder with coin, you want it to work on 4 drops or higher and Shredder is guaranteed to die. Very good value there and it's a possible play that can happen often. Many similar situations are possible, pretty good.
Fallen Hero, I think even this could get some use in constructed, being able to deal 2 damage you can kill annoying stuff like knife jugglers with. It's not terrible, it might take a removal even. About as good as sorcerer's apprentice early game, maybe even better at times, late game when you might not have spells or avoiding using spells early game saving you a frost bolt even? when 2 damage for 2 could remove a lot. I would want to have this card but not for synergy. It's better to have this for control mages than apprentice I think.
Coldarra Drake, well I don't think any one will use good hard earned dust to craft this epic. It's so slow to be usable. Can be good for arena.
GvG had 8 cards per class, so I hope we see 5 more for mage.
Neutral cards that have synergy with those two. No one will play maiden, it's really no value. Saraad is too slow and costly to give any value, at best you can get 1 spell from it which could be junk all of that for 7 mana. synergy here is too slow to be worthwhile. so far.
----
good to see some cheap legs though, wonder what they will do, they must have some big draw backs.