Echo wrote "I don't see this deck doing well considering it is so focused on doing one thing", but I actually think that the deck that might break the game will be more degenerate than this, focusing entirely on the early turns and not even playing ramp + Mountseller.

In any case, don't disenchant your extra copies of Gibberling and Voracious Reader.

If you used your hero power on turn 2, you can clear a 3-health minion on turn 3, which increases the chance this lives to turn 4.

Combines well with Argent Braggart.

Reminds me of Burly Rockjaw Trogg. That one wasn't resilient enough to grow out of control. This has 2 health more, plus it still gets some benefit if it's killed by a spell. But it's also one mana extra, so I'm not convinced it is enough of an improvement.

I can see this being played in a Zoolock with Magic Carpet, EVIL Genius and Disciplinarian Gandling. Or perhaps in a deck with Brittlebone Destroyer and Flesh Giant.

I wonder if they didn't make this 3 mana because they want all Ragers to be bad, or whether they found that it was actually too strong at 3 mana while play testing.

...unless you're Warlock.

It comes close to pre-nerf Battlefiend, so definitely good and maybe OP.

This may be playable in a super low curve Token Druid. Perhaps not feasible in Standard, but in Wild there is Living Roots and Mark of the Lotus to enable that archetype.

I play Oaken Summons a lot in Jungle Giants Druid and after quest completion it can pull any minion from your deck. Of course you never know for sure in Hearthstone whether a similar card will work in a similar way, but in the case of Jungle Giants the discounted cards cost 0 while in the deck. I haven't played Oaken Summons plus Embiggen though.

Edit: Made it clear that I'm certain about the Oaken Summons interaction with Jungle Giants; logically Oaken Summons and Embiggen should interact the same but I haven't tested that.

Unless they programmed an order specifically for this card, I think it will be the oldest minion first (like deathrattles).

You can still use one-sided AoE, like Breath of the Infinite and Holy Nova.

You could play Embiggen, then Guardian Animals, then the second Embiggen. If you have a lot of card draw, it doesn't really matter that you can't use your second copy of Guardian Animals, while if you don't have a lot of card draw, chances are that you either won't draw your second Embiggen or your second Guardian Animals.

Pulling Zixor and a Tiger is not bad though, since you'd shuffle the prime into your deck at a time when you have enough mana to summon it when drawn.

Technically they also have Druid of the Claw, but that only becomes a beast after you pick a form, so it cannot be pulled by this spell either.

If you buff with Embiggen, you increase the cost of the minions in your deck. Unlike variable cost changes on for example giants and Shirvallah, the Tiger, fixed cost changes are applied in-deck. So you'd have to put 4-cost beasts in your deck in order to pull them after casting Embiggen once.

Deck thinning is good, but except in extreme cases (Mysterious Challenger) you don't really want to put cards in your deck that are bad on curve just to be able to pull them. Most of the cheap beasts worth playing in Standard have battlecries and already have rush, so they're missing a lot of value when pulled.

One exception could be Bad Luck Albatross: if you pull one or two of those, your future draws will be significantly better than your opponent's. But ever since it was nerfed, it's not great when played on curve.

If your deck runs Kael'thas Sunstrider, you have a chance to thin your deck for 0 mana, in which case it doesn't matter much if the beasts you pull are skipping their battlecries.

Are you talking about Sap? While annoying to see 9 mana undone, the opponent is using 2 mana and the most versatile card in their deck, so it's not a total loss. Specifically against control, the tempo loss may not be fatal. For Rattlegore, there is always the option to shuffle bombs to turn off their Zephrys off. In theory Bad Luck Albatross allows Demon Hunter to do that too, but since its nerf that's no longer a good card to play on curve.

The point of the comparison was that copying cards from the enemy deck is pretty useful, provided that you don't pay too much for that ability.

If you can copy three cards, you get the best pick from discover plus two others. And since they are discounted to 1, any bad cards won't be clogging your hand. But that is assuming you can copy three cards, which may not be possible in Standard right now.

You are right that it is much harder to use the cards you copied in the same turn with Keymaster. I used Operative mostly to fish for value; copying Death Knights was fun. But having the option to copy something to use immediately can be useful at times.

How is this bad with Pit Commander? Sure, you'll have to wait another turn for its ability to trigger, but you get a free 10/10.