The 6/3 can be good in classes like Mage, Druid, Priest and generally decks that want to outgrind their opponent.
It actually fits very well in Ramp Druid, which can get it out early and generally hero powers a lot in certain matchups (like Hunter). Also Druid has the greatest benefit from this, as it doubles the damage and the armor gain.
Mage needs a controlling archetype for it to shine, it's obviously bad in face rushing decks or Freeze, but they seem to push the hero power Mage agenda a lot with their cards.
It's also very powerful in Priest, don't underestimate the benefit of 4 heal (/damage with Auchenai). Velen could actually be a card if it wouldn't be BGH fodder. Good potential here.
Paladin could be interesting, maybe if they add more Silverhand Recruit synergys.
I think it will be rather bad in Warrior because the armor doesn't affect the board in any way and you have enough Shield Slam enablers anyway. It won't affect the outcome of the match most of the time.
Don't think it's good for Rogue either, you can only hit enemies a limited amount of time before dying, you are generally looking for a combo/tempo finish. And you are buffing your weapon anyway, a +1 doesn't do that much in that case.
I doubt it's worth it in Shaman, the class is generally not known for outgrinding opponents but riding it's tempo to a victory or losing. The benefit is not that great either.
It's total shit for Warlock and Hunter.
Good: Druid, Priest, maybe Mage
Mediocre (might have potential): Paladin, maybe Shaman (unlikely)
Bad: Warrior, Rogue
Terribad: Warlock, Hunter
I don't really buy the "dies to random shit" argument, it shines in grindy control decks that usually employ a plethora of methods to survive the early game and clear the board. These decks can afford the bad stats when they get their value back down the line.
Pretty sure this sees constructed play in SOME way.
AMG: I think the problem with this is that Echo Giants Mage is generally a rather bad deck that thrives on it's unusual plays and deceiving the opponent to win. The deck needs it's opponent to not know the matchup and misplay. I don't think Frozen Giant can solve this, as the setup is so excruciatingly slow that you will usually run out of control before you get value out of them. That will probably not stop people to try it and steal some games with it, but generally not that great.
Frozen Giant just seems like garbage overall.
